Ceramic Encapsulation of an Implantable Device

ABSTRACT

An implantable device is provided. The implantable device may include a flexible carrier configured for implantation in a subject, at least one pair of modulation electrodes associated with the carrier, an antenna configured to receive an electrical signal disposed on the flexible carrier, a circuit electrically coupling the antenna to the at least one pair of modulation electrodes; and a ceramic housing. At least one of the antenna and the circuit may be located within the ceramic housing.

RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119(e)to U.S. Provisional Application No. 61/836,089, filed Jun. 17, 2013,which is incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to devices andmethods for modulating a nerve. More particularly, embodiments of thepresent disclosure relate to devices and methods for modulating a nervethrough the delivery of energy via an implantable electrical modulator.

BACKGROUND

Neural modulation presents the opportunity to treat many physiologicalconditions and disorders by interacting with the body's own naturalneural processes. Neural modulation includes inhibition (e.g. blockage),stimulation, modification, regulation, or therapeutic alteration ofactivity, electrical or chemical, in the central, peripheral, orautonomic nervous system. By modulating the activity of the nervoussystem, for example through the stimulation of nerves or the blockage ofnerve signals, several different goals may be achieved. Motor neuronsmay be stimulated at appropriate times to cause muscle contractions.Sensory neurons may be blocked, for instance to relieve pain, orstimulated, for instance to provide a signal to a subject. In otherexamples, modulation of the autonomic nervous system may be used toadjust various involuntary physiological parameters, such as heart rateand blood pressure. Neural modulation may provide the opportunity totreat several diseases or physiological conditions, a few examples ofwhich are described in detail below.

Among the conditions to which neural modulation may be applied are sleeprelated breathing disorders, such as snoring and obstructive sleep apnea(OSA). OSA is a respiratory disorder characterized by recurrent episodesof partial or complete obstruction of the upper airway during sleep.During the sleep of a person without OSA, the pharyngeal muscles relaxduring sleep and gradually collapse, narrowing the airway. The airwaynarrowing limits the effectiveness of the sleeper's breathing, causing arise in CO₂ levels in the blood. The increase in CO₂ results in thepharyngeal muscles contracting to open the airway to restore properbreathing. The largest of the pharyngeal muscles responsible for upperairway dilation is the genioglossus muscle, which is one of severaldifferent muscles in the tongue. The genioglossus muscle is responsiblefor forward tongue movement and the stiffening of the anteriorpharyngeal wall. In patients with OSA, the neuromuscular activity of thegenioglossus muscle is decreased compared to normal individuals,accounting for insufficient response and contraction to open the airwayas compared to a normal individual. This lack of response contributes toa partial or total airway obstruction, which significantly limits theeffectiveness of the sleeper's breathing. In OSA patients, there areoften several airway obstruction events during the night. Because of theobstruction, there is a gradual decrease of oxygen levels in the blood(hypoxemia). Hypoxemia leads to night time arousals, which may beregistered by EEG, showing that the brain awakes from any stage of sleepto a short arousal. During the arousal, there is a conscious breath orgasp, which resolves the airway obstruction. An increase in sympathetictone activity rate through the release of hormones such as epinephrineand noradrenaline also often occurs as a response to hypoxemia. As aresult of the increase in sympathetic tone, the heart enlarges in anattempt to pump more blood and increase the blood pressure and heartrate, further arousing the patient. After the resolution of the apneaevent, as the patient returns to sleep, the airway collapses again,leading to further arousals.

These repeated arousals, combined with repeated hypoxemia, leaves thepatient sleep deprived, which leads to daytime somnolence and worsenscognitive function. This cycle can repeat itself up to hundreds of timesper night in severe patients. Thus, the repeated fluctuations in andsympathetic tone and episodes of elevated blood pressure during thenight evolve to high blood pressure through the entire day.Subsequently, high blood pressure and increased heart rate may causeother diseases.

Snoring in patients is frequently a result of a partially obstructedairway. Some patients experience relaxation of the pharyngeal muscles toa point that involves partial obstruction not significant enough tocause subsequent arousals during sleep. When the pharyngeal musclesrelax and narrow the airway, air must travel through the airway at ahigher velocity to maintain a similar volumetric flow rate. Highervelocity flows are more likely to be turbulent. These turbulent flowscan cause vibrations in the tissue structure of the airway, producing anaudible snoring effect. Snoring may have several adverse effects on bothsufferers and those around them. Snoring may lead to hypopnea, acondition in which blood oxygen levels are decreased, resulting inshallower, less restful sleep. Snoring may also be associated with anincreased risk of stroke and carotid artery atherosclerosis.Additionally, snoring may be detrimental to the sleep of those aroundthe sufferer.

Efforts for treating both snoring and OSA include Continuous PositiveAirway Pressure (CPAP) treatment, which requires the patient to wear amask through which air is blown into the nostrils to keep the airwayopen. Other treatment options include the implantation of rigid insertsin the soft palate to provide structural support, tracheotomies, ortissue ablation.

Another condition to which neural modulation may be applied is theoccurrence of migraine headaches. Pain sensation in the head istransmitted to the brain via the occipital nerve, specifically thegreater occipital nerve, and the trigeminal nerve. When a subjectexperiences head pain, such as during a migraine headache, theinhibition of these nerves may serve to decrease or eliminate thesensation of pain.

Neural modulation may also be applied to hypertension. Blood pressure inthe body is controlled via multiple feedback mechanisms. For example,baroreceptors in the carotid body in the carotid artery are sensitive toblood pressure changes within the carotid artery. The baroreceptorsgenerate signals that are conducted to the brain via theglossopharyngeal nerve when blood pressure rises, signaling the brain toactivate the body's regulation system to lower blood pressure, e.g.through changes to heart rate, and vasodilation/vasoconstriction.Conversely, parasympathetic nerve fibers on and around the renalarteries generate signals that are carried to the kidneys to initiateactions, such as salt retention and the release of angiotensin, whichraise blood pressure. Modulating these nerves may provide the ability toexert some external control over blood pressure.

The foregoing are just a few examples of conditions to whichneuromodulation may be of benefit, however embodiments of the inventiondescribed hereafter are not necessarily limited to treating only theabove-described conditions.

SUMMARY

Some embodiments may include an implantable device. The implantabledevice may include a flexible carrier configured for implantation in asubject, at least one pair of modulation electrodes associated with thecarrier, an antenna configured to receive an electrical signal disposedon the flexible carrier, a circuit electrically coupling the antenna tothe at least one pair of modulation electrodes; and a ceramic housing.At least one of the antenna and the circuit may be located within theceramic housing.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the embodiments disclosed herein.

FIG. 1 schematically illustrates an implant unit and external unit,according to an exemplary embodiment of the present disclosure.

FIG. 2 is a partially cross-sectioned side view of a subject with animplant unit and external unit, according to an exemplary embodiment ofthe present disclosure.

FIG. 3 schematically illustrates a system including an implant unit andan external unit, according to an exemplary embodiment of the presentdisclosure.

FIGS. 4 a and 4 b illustrate an exemplary embodiment of an externalunit.

FIGS. 5 a and 5 b illustrate a double-layer crossover antenna.

FIG. 6 a illustrates an embodiment of a carrier as viewed from thebottom.

FIG. 6 b illustrates an embodiment of a carrier in cross section.

FIG. 7 illustrates an embodiment of a carrier including removable tabs.

FIGS. 8 a-f illustrate alternate embodiments of a carrier andelectronics housing.

FIG. 9 illustrates a medical device console unit of an exemplaryembodiment of the present disclosure.

FIG. 10 is a top view of an implant unit, according to an exemplaryembodiment of the present disclosure.

FIGS. 11 a-b are a top views of alternate embodiments of implant unit,according to an exemplary embodiment of the present disclosure.

FIG. 12 illustrates additional features of an exemplary embodiment of animplant unit according to the present disclosure

FIG. 13 illustrates a ceramic implant housing of an exemplary embodimentof the present disclosure.

FIG. 14 illustrates circuitry of an implant unit and an external unit,according to an exemplary embodiment of the present disclosure.

FIG. 15 a illustrates a pair of electrodes spaced apart from one anotheralong the longitudinal direction of nerve to facilitate generation of anelectric field having field lines substantially parallel to thelongitudinal direction of nerve.

FIG. 15 b illustrates an embodiment wherein electrodes are spaced apartfrom one another in a longitudinal direction of at least a portion ofnerve.

FIG. 15 c illustrates a situation wherein electrodes are spaced apartfrom one another in a transverse direction of nerve.

FIG. 16 illustrates effects of electrode configuration on the shape of agenerated electric field.

FIG. 17 depicts the composition of an exemplary modulation pulse train.

FIG. 18 illustrates a graph of quantities that may be used indetermining energy delivery as a function coupling, according to anexemplary disclosed embodiment.

FIG. 19 depicts anatomy of the tongue and associated muscles and nerves.

FIG. 20 illustrates an exemplary implantation position for an implantunit.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Embodiments of the present disclosure relate generally to a device formodulating a nerve through the delivery of energy. Nerve modulation, orneural modulation, includes inhibition (e.g. blockage), stimulation,modification, regulation, or therapeutic alteration of activity,electrical or chemical, in the central, peripheral, or autonomic nervoussystem. Nerve modulation may take the form of nerve stimulation, whichmay include providing energy to the nerve to create a voltage changesufficient for the nerve to activate, or propagate an electrical signalof its own. Nerve modulation may also take the form of nerve inhibition,which may including providing energy to the nerve sufficient to preventthe nerve from propagating electrical signals. Nerve inhibition may beperformed through the constant application of energy, and may also beperformed through the application of enough energy to inhibit thefunction of the nerve for some time after the application. Other formsof neural modulation may modify the function of a nerve, causing aheightened or lessened degree of sensitivity. As referred to herein,modulation of a nerve may include modulation of an entire nerve and/ormodulation of a portion of a nerve. For example, modulation of a motorneuron may be performed to affect only those portions of the neuron thatare distal of the location to which energy is applied.

In patients that suffer from a sleep breathing disorder, for example, aprimary target response of nerve stimulation may include contraction ofa tongue muscle (e.g., the muscle) in order to move the tongue to aposition that does not block the patient's airway. In the treatment ofmigraine headaches, nerve inhibition may be used to reduce or eliminatethe sensation of pain. In the treatment of hypertension, neuralmodulation may be used to increase, decrease, eliminate or otherwisemodify nerve signals generated by the body to regulate blood pressure.

While embodiments of the present disclosure may be disclosed for use inpatients with specific conditions, the embodiments may be used inconjunction with any patient/portion of a body where nerve modulationmay be desired. That is, in addition to use in patients with a sleepbreathing disorder, migraine headaches, or hypertension, embodiments ofthe present disclosure may be used in many other areas, including, butnot limited to: deep brain stimulation (e.g., treatment of epilepsy,Parkinson's, and depression); cardiac pace-making, stomach musclestimulation (e.g., treatment of obesity), back pain, incontinence,menstrual pain, and/or any other condition that may be affected byneural modulation.

FIG. 1 illustrates an implant unit and external unit, according to anexemplary embodiment of the present disclosure. An implant unit 110, maybe configured for implantation in a subject, in a location that permitsit to modulate a nerve 115. The implant unit 110 may be located in asubject such that intervening tissue 111 exists between the implant unit110 and the nerve 115. Intervening tissue may include muscle tissue,connective tissue, organ tissue, or any other type of biological tissue.Thus, location of implant unit 110 does not require contact with nerve115 for effective neuromodulation. The implant unit 110 may also belocated directly adjacent to nerve 115, such that no intervening tissue111 exists.

In treating a sleep breathing disorder, implant unit 110 may be locatedon a genioglossus muscle of a patient. Such a location is suitable formodulation of the hypoglossal nerve, branches of which run inside thegenioglossus muscle. Implant unit 110 may also be configured forplacement in other locations. For example, migraine treatment mayrequire subcutaneous implantation in the back of the neck, near thehairline of a subject, or behind the ear of a subject, to modulate thegreater occipital nerve and/or the trigeminal nerve. Treatinghypertension may require the implantation of a neuromodulation implantintravascularly inside the renal artery or renal vein (to modulate theparasympathetic renal nerves), either unilaterally or bilaterally,inside the carotid artery or jugular vein (to modulate theglossopharyngeal nerve through the carotid baroreceptors). Alternativelyor additionally, treating hypertension may require the implantation of aneuromodulation implant subcutaneously, behind the ear or in the neck,for example, to directly modulate the glossopharyngeal nerve.

External unit 120 may be configured for location external to a patient,either directly contacting, or close to the skin 112 of the patient.External unit 120 may be configured to be affixed to the patient, forexample, by adhering to the skin 112 of the patient, or through a bandor other device configured to hold external unit 120 in place. Adherenceto the skin of external unit 120 may occur such that it is in thevicinity of the location of implant unit 110.

FIG. 2 illustrates an exemplary embodiment of a neuromodulation systemfor delivering energy in a patient 100 with a sleep breathing disorder.The system may include an external unit 120 that may be configured forlocation external to the patient. As illustrated in FIG. 2, externalunit 120 may be configured to be affixed to the patient 100. FIG. 2illustrates that in a patient 100 with a sleep breathing disorder, theexternal unit 120 may be configured for placement underneath thepatient's chin and/or on the front of patient's neck. The suitability ofplacement locations may be determined by communication between externalunit 120 and implant unit 110, discussed in greater detail below. Inalternate embodiments, for the treatment of conditions other than asleep breathing disorder, the external unit may be configured to beaffixed anywhere suitable on a patient, such as the back of a patient'sneck, i.e. for communication with a migraine treatment implant unit, onthe outer portion of a patient's abdomen, i.e. for communication with astomach modulating implant unit, on a patient's back, i.e. forcommunication with a renal artery modulating implant unit, and/or on anyother suitable external location on a patient's skin, depending on therequirements of a particular application.

External unit 120 may further be configured to be affixed to analternative location proximate to the patient. For example, in oneembodiment, the external unit may be configured to fixedly or removablyadhere to a strap or a band that may be configured to wrap around a partof a patient's body. Alternatively, or in addition, the external unitmay be configured to remain in a desired location external to thepatient's body without adhering to that location.

The external unit 120 may include a housing. The housing may include anysuitable container configured for retaining components. In addition,while the external unit is illustrated schematically in FIG. 2, thehousing may be any suitable size and/or shape and may be rigid orflexible. Non-limiting examples of housings for the external unit 100include one or more of patches, buttons, or other receptacles havingvarying shapes and dimensions and constructed of any suitable material.In one embodiment, for example, the housing may include a flexiblematerial such that the external unit may be configured to conform to adesired location. For example, as illustrated in FIG. 2, the externalunit may include a skin patch, which, in turn, may include a flexiblesubstrate. The material of the flexible substrate may include, but isnot limited to, plastic, silicone, woven natural fibers, and othersuitable polymers, copolymers, and combinations thereof. Any portion ofexternal unit 120 may be flexible or rigid, depending on therequirements of a particular application.

As previously discussed, in some embodiments external unit 120 may beconfigured to adhere to a desired location. Accordingly, in someembodiments, at least one side of the housing may include an adhesivematerial. The adhesive material may include a biocompatible material andmay allow for a patient to adhere the external unit to the desiredlocation and remove the external unit upon completion of use. Theadhesive may be configured for single or multiple uses of the externalunit. Suitable adhesive materials may include, but are not limited tobiocompatible glues, starches, elastomers, thermoplastics, andemulsions.

FIG. 3 schematically illustrates a system including external unit 120and an implant unit 110. In some embodiments, internal unit 110 may beconfigured as a unit to be implanted into the body of a patient, andexternal unit 120 may be configured to send signals to and/or receivesignals from implant unit 110.

As shown in FIG. 3, various components may be included within a housingof external unit 120 or otherwise associated with external unit 120. Asillustrated in FIG. 3, at least one processor 144 may be associated withexternal unit 120. For example, the at least one processor 144 may belocated within the housing of external unit 120. In alternativeembodiments, the at least one processor may be configured for wired orwireless communication with the external unit from a location externalto the housing.

The at least one processor may include any electric circuit that may beconfigured to perform a logic operation on at least one input variable.The at least one processor may therefore include one or more integratedcircuits, microchips, microcontrollers, and microprocessors, which maybe all or part of a central processing unit (CPU), a digital signalprocessor (DSP), a field programmable gate array (FPGA), or any othercircuit known to those skilled in the art that may be suitable forexecuting instructions or performing logic operations.

FIG. 3 illustrates that the external unit 120 may further be associatedwith a power source 140. The power source may be removably couplable tothe external unit at an exterior location relative to external unit.Alternatively, as shown in FIG. 3, power source 140 may be permanentlyor removably coupled to a location within external unit 120. The powersource may further include any suitable source of power configured to bein electrical communication with the processor. In one embodiment, forexample the power source 140 may include a battery.

The power source may be configured to power various components withinthe external unit. As illustrated in FIG. 3, power source 140 may beconfigured to provide power to the processor 144. In addition, the powersource 140 may be configured to provide power to a signal source 142.The signal source 142 may be in communication with the processor 144 andmay include any device configured to generate a signal (e.g., asinusoidal signal, square wave, triangle wave, microwave,radio-frequency (RF) signal, or any other type of electromagneticsignal). Signal source 142 may include, but is not limited to, awaveform generator that may be configured to generate alternatingcurrent (AC) signals and/or direct current (DC) signals. In oneembodiment, for example, signal source 142 may be configured to generatean AC signal for transmission to one or more other components. Signalsource 142 may be configured to generate a signal of any suitablefrequency. In some embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 6.5 MHz to about 13.6MHz. In additional embodiments, signal source 142 may be configured togenerate a signal having a frequency of from about 7.4 to about 8.8 MHz.In further embodiments, signal source 142 may generate a signal having afrequency as low as 90 kHz or as high as 28 MHz.

Signal source 142 may be configured for direct or indirect electricalcommunication with an amplifier 146. The amplifier may include anysuitable device configured to amplify one or more signals generated fromsignal source 142. Amplifier 146 may include one or more of varioustypes of amplification devices, including, for example, transistor baseddevices, operational amplifiers, RF amplifiers, power amplifiers, or anyother type of device that can increase the gain associated one or moreaspects of a signal. The amplifier may further be configured to outputthe amplified signals to one or more components within external unit120.

External unit may 120 additionally include a memory unit 143. Processor144 may communicate with memory unit 143, for example, to store andretrieve data. Stored and retrieved data may include, for example,information about therapy parameters and information about implant unit110 and external unit 120. The use of memory unit 143 is explained ingreater detail below. Memory unit 143 may be any suitable for ofnon-transient computer readable storage medium,

External unit 120 may also include communications interface 145, whichmay be provided to permit external unit 120 to communicate with otherdevices, such as programming devices and data analysis device. Furtherdetails regarding communications interface 145 are included below.

The external unit may additionally include a primary antenna 150. Theprimary antenna may be configured as part of a circuit within externalunit 120 and may be coupled either directly or indirectly to variouscomponents in external unit 120. For example, as shown in FIG. 3,primary antenna 150 may be configured for communication with theamplifier 146.

The primary antenna may include any conductive structure that may beconfigured to create an electromagnetic field. The primary antenna mayfurther be of any suitable size, shape, and/or configuration. The size,shape, and/or configuration may be determined by the size of thepatient, the placement location of the implant unit, the size and/orshape of the implant unit, the amount of energy required to modulate anerve, a location of a nerve to be modulated, the type of receivingelectronics present on the implant unit, etc. The primary antenna mayinclude any suitable antenna known to those skilled in the art that maybe configured to send and/or receive signals. Suitable antennas mayinclude, but are not limited to, a long-wire antenna, a patch antenna, ahelical antenna, etc. In one embodiment, for example, as illustrated inFIG. 3, primary antenna 150 may include a coil antenna. Such a coilantenna may be made from any suitable conductive material and may beconfigured to include any suitable arrangement of conductive coils(e.g., diameter, number of coils, layout of coils, etc.). A coil antennasuitable for use as primary antenna 150 may have a diameter of betweenabout 1 cm and 10 cm, and may be circular or oval shaped. In someembodiments, a coil antenna may have a diameter between 5 cm and 7 cm,and may be oval shaped. A coil antenna suitable for use as primaryantenna 150 may have any number of windings, e.g. 4, 8, 12, or more. Acoil antenna suitable for use as primary antenna 150 may have a wirediameter between about 0.1 mm and 2 mm. These antenna parameters areexemplary only, and may be adjusted above or below the ranges given toachieve suitable results.

As noted, implant unit 110 may be configured to be implanted in apatient's body (e.g., beneath the patient's skin). FIG. 2 illustratesthat the implant unit 110 may be configured to be implanted formodulation of a nerve associated with a muscle of the subject's tongue130. Modulating a nerve associated with a muscle of the subject's tongue130 may include stimulation to cause a muscle contraction. In furtherembodiments, the implant unit may be configured to be placed inconjunction with any nerve that one may desire to modulate. For example,modulation of the occipital nerve, the greater occipital nerve, and/orthe trigeminal nerve may be useful for treating pain sensation in thehead, such as that from migraines. Modulation of parasympathetic nervefibers on and around the renal arteries (i.e. the renal nerves), thevagus nerve, and/or the glossopharyngeal nerve may be useful fortreating hypertension. Additionally, any nerve of the peripheral nervoussystem (both spinal and cranial), including motor neurons, sensoryneurons, sympathetic neurons and parasympathetic neurons, may bemodulated to achieve a desired effect.

Implant unit 110 may be formed of any materials suitable forimplantation into the body of a patient. In some embodiments, implantunit 110 may include a flexible carrier 161 (FIG. 4) including aflexible, biocompatible material. Such materials may include, forexample, silicone, polyimides, phenyltrimethoxysilane (PTMS), polymethylmethacrylate (PMMA), Parylene C, polyimide, liquid polyimide, laminatedpolyimide, black epoxy, polyether ether ketone (PEEK), Liquid CrystalPolymer (LCP), Kapton, etc. Implant unit 110 may further includecircuitry including conductive materials, such as gold, platinum,titanium, or any other biocompatible conductive material or combinationof materials. Implant unit 110 and flexible carrier 161 may also befabricated with a thickness suitable for implantation under a patient'sskin. Implant 110 may have thickness of less than about 4 mm or lessthan about 2 mm.

Other components that may be included in or otherwise associated withthe implant unit are illustrated in FIG. 3. For example, implant unit110 may include a secondary antenna 152 mounted onto or integrated withflexible carrier 161. Similar to the primary antenna, the secondaryantenna may include any suitable antenna known to those skilled in theart that may be configured to send and/or receive signals. The secondaryantenna may include any suitable size, shape, and/or configuration. Thesize, shape and/or configuration may be determined by the size of thepatient, the placement location of the implant unit, the amount ofenergy required to modulate the nerve, etc. Suitable antennas mayinclude, but are not limited to, a long-wire antenna, a patch antenna, ahelical antenna, etc. In some embodiments, for example, secondaryantenna 152 may include a coil antenna having a circular shape (see alsoFIG. 10) or oval shape. Such a coil antenna may be made from anysuitable conductive material and may be configured to include anysuitable arrangement of conductive coils (e.g., diameter, number ofcoils, layout of coils, etc.). A coil antenna suitable for use assecondary antenna 152 may have a diameter of between about 5 mm and 30mm, and may be circular or oval shaped. A coil antenna suitable for useas secondary antenna 152 may have any number of windings, e.g. 4, 15,20, 30, or 50. A coil antenna suitable for use as secondary antenna 152may have a wire diameter between about 0.01 mm and 1 mm. These antennaparameters are exemplary only, and may be adjusted above or below theranges given to achieve suitable results.

FIGS. 4 a and 4 b illustrate an exemplary embodiment of external unit120, including features that may be found in any combination in otherembodiments. FIG. 4 a illustrates a side view of external unit 120,depicting carrier 1201 and electronics housing 1202.

Carrier 1201 may include a skin patch configured for adherence to theskin of a subject, for example through adhesives of mechanical means.Carrier 1201 may be flexible or rigid, or may have flexible portions andrigid portions. Carrier 1201 and may include a primary antenna 150, forexample, a double-layer crossover antenna 1101 such as that illustratedin FIGS. 5 a and 5 b. Carrier 1201 may also include power source 140,such as a paper battery, thin film battery, or other type ofsubstantially flat and/or flexible battery. Carrier 1201 may alsoinclude any other type of battery or power source. Carrier 1201 may alsoinclude a connector 1203 configured for selectively or removablyconnecting carrier 1201 to electronics housing 1202. Connector 1203 mayextend or protrude from carrier 1201. Connector 1203 may be configuredto be received by a recess 1204 of electronics housing 1202 Connector1203 may be configured as a non-pouch connector, configured to provide aselective connection to electronics housing 1204 without the substantialuse of concave feature. Connector 1203 may include, for example a peg,and may have flexible arms. Connector 1203 may further include amagnetic connection, a velcro connection, and/or a snap dome connection.Connector 1203 may also include a locating feature, configured to locateelectronics housing 1202 at a specific height, axial location, and/oraxial orientation with respect to carrier 1201. A locating feature ofconnector 1203 may further include pegs, rings, boxes, ellipses, bumps,etc. Connector 1203 may be centered on carrier 1201, may be offset fromthe center by a predetermined amount, or may be provided at any othersuitable location of carrier 1201. Multiple connectors 1203 may beprovided on carrier 1201. Connector 1203 may be configured such thatremoval from electronics housing 1202 causes breakage of connector 1203.Such a feature may be desirable to prevent re-use of carrier 1201, whichmay lose some efficacy through continued use.

Direct contact between primary antenna 150 and the skin of a subject mayresult in alterations of the electrical properties of primary antenna150. This may be due to two effects. First, the skin of a subject is aresistive volume conductor, and creating electrical contact betweenprimary antenna 150 and the skin may result in the skin becoming part ofan electric circuit including the primary antenna. Thus, when primaryantenna 150 is energized, current may flow through the skin, alteringthe electrical properties of primary antenna 150. Second, when thesubject sweats, the generated moisture may also act as a resistiveconductor, creating electrical pathways that did not exist previously.These effects may occur even when there is no direct contact between theprimary antenna 150 and the skin, for example, when an adhesive layer isinterposed between the primary antenna 150 and the skin. Because manyadhesives are not electrically insulating, and may absorb moisture froma subject's skin, these effects can occur without direct contact betweenthe antenna and the skin. In some embodiments, processor 144 may beconfigured to detect the altered properties of primary antenna 150 andtake these into account when generating modulation and sub-modulationcontrol signals for transmission to an implant unit 110.

In some embodiments, carrier 1201 may include a buffered antenna, asillustrated in FIGS. 6 a-b and 22 (not drawn to scale), to counteract(e.g., reduce or eliminate) the above-described effects. FIG. 6 aillustrates an embodiment of carrier 1201 as viewed from the bottom.FIG. 6 b illustrates an embodiment of carrier 1201 in cross section.Carrier 1201 may include one or more structures for separating anantenna from the skin of a subject. In some embodiments, carrier 1201may include a buffer layer 2150 that provides an air gap 2160 betweenthe skin of a subject and the antenna. Carrier 1201 may also include atop layer 2130 and a top center region 2140.

As illustrated in FIGS. 6 a-b, buffer layer 2150 may be disposed on theflexible carrier at a position so as to be between the antenna and theskin of the subject when carrier 1201 is in use. Buffer layer 2150 mayinclude any suitable material or structure to provide or establish anair gap 2160 between the antenna 150 and the skin of the subject. Asused herein, air gap 2160 may include any space, area, or region betweenthe skin of the subject and antenna 150 not filled by a solid material.In some embodiments, buffer layer 2150 may include a single layer. Inother embodiments, buffer layer 2150 may include multiple sub-layers(e.g., two, three, or more sub-layers). In still other embodiments,buffer layer 2150 may include an extension of one or more structuresassociated with carrier 1201 in order to move antenna 150 away from asubject's skin.

The air gap 2160 provided may be contiguous or may reside within oramong various structures associated with buffer layer 2150. For example,in some embodiments, air gap 2160 may include a space or region free orrelatively free of structures, such as air gap 2160 shown in FIG. 6 b,which includes an air filled volume created between the skin of thesubject and antenna 150 by the structure of buffer layer 2150. In otherembodiments, air gap 2160 may be formed within or between structuresassociated with buffer layer 2150. For example, air gap 2160 may beformed by one or more porous materials, including open or close cellfoams, fibrous mats, woven materials, fabrics, perforated sheetmaterials, meshes, or any other material or structure having air spaceswithin boundaries of the material or structure. Further, buffer layer2150 may include dielectric materials, hydrophobic closed cell foams,open celled foams, cotton and other natural fibers, porous cellulosebased materials, synthetic fibers, and any other material or structuresuitable for establishing air gap 2160.

Air gap 2160 need not contain only air. Rather, other materials, fluids,or gases may be provided within air gap 2160. For example, in somecases, air gap 2160 may include carbon dioxide, nitrogen, argon, or anyother suitable gases or materials.

FIGS. 6 a and 6 b provide a diagrammatic depiction of a carrier 1201including an exemplary buffer layer 2150, consistent with the presentdisclosure. In the structure shown if FIGS. 6 a and 6 b, air gap 2160 isprovided by a buffer layer 2150 having multiple sub-layers.Specifically, buffer layer 2150 may include a separation sub-layer 2110and an adhesive sub-layer 2120. Separation sub-layer 2110, which may ormay not be included in buffer layer 2150, may include any structure forisolating or otherwise separating antenna 150 from a surface of thesubject's skin. In the embodiment shown in FIGS. 6 a and 6 b, air gap2160 may be established through patterning of adhesive sub-layer 2120.For example, as shown, adhesive sub-layer 2120 may be disposed around aperimeter of separation sub-layer 2110, and air gap 2160 may beestablished in a region in the middle of adhesive sub-layer 2120. Ofcourse, other configurations of adhesive sub-layer 2120 may also bepossible. For example, air gap 2160 may be formed between any pattern offeatures associated with adhesive sub-layer 2120, including, forexample, adhesive stripes, dots, meshes, etc. For example, adhesivesub-layer 2120 may include a series of discrete adhesive dots or lines,a mesh-pattern of adhesive material, or any other pattern suitable forestablishing air gap 2160

While in some embodiments, air gap 2160 may be established by adhesivesub-layer 2120 or by any other sub-layer of buffer layer 2150, in otherembodiments, air gap 2160 may be established by separation sub-layer2110. In such embodiments, separation sub-layer 2110 may be made toinclude various patterns (e.g., perforations, meshes, islands, bumps,pillars, etc.) to provide air gap 2160. Separation sub-layer 2110 mayalso be formed of a various types of materials. For example, separationsub-layer 2110 may include open or closed cell foam, fabric, paper,perforated sheet materials, or any other material suitable for providingair gaps or spaces therewithin. Separation sub-layer 2110 may be formedof insulating material, such as a dielectric material.

In some embodiments, buffer layer 2150 may be formed by extensions ofanother layer (e.g., a top layer 2130) associated with carrier 1201. Forexample, top layer 2130 may include legs or extension portions thatextend below antenna 150 such that when in use, antenna 150 ispositioned at a location above the subject's skin.

Air gap 2160 may have any suitable dimensions. In some embodiments, airgap 2160 may be between 250 microns 1 mm in height. In other embodimentsair gap 2160 may be between 1 mm and 5 mm in height.

The buffered antenna, as illustrated in FIGS. 6 a and 6 b may serve toelectrically insulate and/or isolate primary antenna 150 from the skinand/or the sweat of a subject, thus eliminating or reducing thealterations to electrical properties of the antenna that may result fromcontact with the skin and/or sweat of the subject. A buffered antennamay be constructed with either or both of buffered layer 2110 and airgap 2160 disposed within window region 2150.

In some embodiments, carrier 1201 may be provided with removable tabs,as shown in FIG. 7 for altering a size of the carrier. Users of carrier1201 differ significantly in size and shape. Some users may have largerneck and/or chin areas, some may have smaller. Some users may findrequire more adhesive area to maintain comfort during a therapeuticperiod. To accommodate various preferences, carrier 1201 may be providedwith removable tabs 2220 at either end, wherein the tabs are providedwith a perforated detachment portion where they connect to the carrier1201. A user who desires the increased adhesive area may leave the tabsintact, while a user desiring a smaller adhesive area may tear the tabs2220 along the perforated detachment portion to remove them. Inalternative embodiments, tabs 2220 may be sized and shape to accommodatethe thumbs of a user. In still other embodiments, non-removable tabssized and shaped to accommodate the thumbs of a user may be provided. Insome embodiments, removable tabs 2220 may be provided without adhesive,to be used during attachment of carrier 1201 and subsequently removed.Non-adhesive removable tabs 2220 may permit a user to hold carrier 1201without accidentally sticking it to their fingers.

Returning now to FIGS. 4 a and 4 b, electronics housing 1202 isillustrated in side view in FIG. 4 a and in a bottom view in FIG. 4 b.Electronics housing 1202 may include electronics portion 1205, which maybe arranged inside electronics housing 1202 in any manner that issuitable. Electronics portion 1205 may include various components,further discussed below, of external unit 120. For example, electronicsportion 1205 may include any combination of at least one processor 144associated with external unit 120, a power source 140, such as abattery, a primary antenna 152, and an electrical circuit 170.Electronics portion 1205 may also include any other component describedherein as associated with external unit 120. Additional components mayalso be recognized by those of skill in the art.

Electronics housing 1202 may include a recess 1204 configured to receiveconnector 1203. Electronics housing 1202 may include at least oneelectrical connector 1210, 1211, 1212. Electrical connectors 1210, 1211,1212 may be arranged with pairs of electrical contacts, as shown in FIG.4 b, or with any other number of electrical contacts. The pair ofelectrical contacts of each electrical connector 1210, 1211, 1212 may becontinuously electrically connected with each other inside of housing1202, such that the pair of electrical contacts represents a singleconnection point to a circuit. In such a configuration, it is onlynecessary that one of the electrical contacts within a pair beconnected. Electrical connectors 1210, 1211, and 1212 may thus includeredundant electrical contacts. The electrical contacts of eachelectrical connector 1210, 1211, 1212 may also represent opposite endsof a circuit, for example, the positive and negative ends of a batterycharging circuit. In an exemplary embodiment, as shown in FIG. 4 b,electrical connectors 1210, 1211, and 1212 are configured so as tomaintain electrical contact with an exposed electrical contact portion1108 independent of an axial orientation of electronics housing 1202.Connection between any or all of electrical connectors 1210, 1211, 1212and exposed electrical contact portions 1108 may thus be established andmaintained irrespective of relative axial positions of carrier 1201 andhousing 1202. Thus, when connector 1203 is received by recess 1204,housing 1202 may rotate with respect to carrier 1201 withoutinterrupting electrical contact between at least one of electricalconnectors 1210, 1211, 1212 and exposed electrical contact portions1108. Axial orientation independence may be achieved, for example,through the use of circular exposed electrical contact portions 1108 andeach of a pair of contacts of electrical connectors 1210, 1211, 1212disposed equidistant from a center of recess 1204 at a radiusapproximately equal to that of a corresponding exposed electricalcontact portion 1108. In this fashion, even if exposed electricalcontact portion 1108 includes a discontinuous circle, at least oneelectrical contact of electrical connectors 1210, 1211, and 1212 maymake contact. In FIG. 4 b, electrical connectors 1210, 1211, 1212 areillustrated as pairs of rectangular electrical contacts. Electricalconnectors 1210, 1211, 1212, however, may include any number ofcontacts, be configured as continuous or discontinuous circles, or haveany other suitable shape or configuration.

One exemplary embodiment may operate as follows. As shown in FIG. 4 b,electronics housing 1202 may include more electrical connectors 1210,1211, 1212, than a carrier 1201 includes exposed electrical contactportions 1108. In the illustrated embodiments, electronics housing 1202includes three electrical connectors 1210, 1211, and 1212, while adouble-layer crossover antenna 1101 includes two exposed electricalcontact portions 1108. In such an embodiment, two electrical connectors1211 and 1212 may be configured with continuously electrically connectedelectrical contacts, such that each connector makes contact with adifferent exposed electrical contact portion 1108, where the exposedelectrical contact portions 1108 represent opposite ends of double layercrossover antenna 1101. Thus, antenna 1101 may be electrically connectedto the electrical components contained in electronics portion 1205. Whenconnected to carrier 1201 in this configuration, electrical connectors1210 may not make contact with any electrodes. In this embodiment,electrical connectors 1210 may be reserved to function as opposite endsof a battery charging circuit, in order to charge a battery contained inelectronics portion 1205 when electronics housing 1202 is not being usedfor therapy. A battery charger unit may be provided with a non-breakableconnector similar to that of non-pouch connector 1203, and configured toengage with recess 1204. Upon engaging with recess 1204, electrodecontacts of the battery charger unit may contact electrical connectors1210 to charge a battery contained within electronics portion 1205.

In an additional embodiment consistent with the present disclosure, anactivator chip may include electronics housing 1202. Processor 144 maybe configured to activate when at least one of electrical connectors1210, 1211, 1212 contact exposed electrical contact portions 1108included in carrier 1201. In this manner, an electronics housing 1202may be charged and left dormant for many days prior to activation.Simply connecting electronics housing 1202 to carrier 1201 (and inducingcontact between an electrical connector 1210, 1211, 1212 and anelectrode portion 1108) may cause the processor to activate. Uponactivation, processor 144 may be configured to enter a specific mode ofoperation, such as a calibration mode (for calibrating the processorafter placement of the carrier on the skin), a placement mode (forassisting a user to properly place the carrier on the skin), and/or atherapy mode (to begin a therapy session). The various modes ofprocessor 144 may include waiting periods at the beginning, end, or atany time during. For example, a placement mode may include a waitingperiod at the end of the mode to provide a period during which a subjectmay fall asleep. A therapy mode may include a similar waiting period atthe beginning of the mode. Additionally or alternatively, processor 144may be configured to provide waiting periods separate from the describedmodes, in order to provide a desired temporal spacing between systemactivities.

In some embodiments, housing 1202 may include features to communicatewith a user. For example, one or more LED lights and/or one or moreaudio devices may be provided. LEDs and audio devices may be provided tocommunicate various pieces of information to a user, such as low batterywarnings, indications of activity, malfunction alerts, indications ofconnectivity (e.g. connections to electrical components on carrier1201).

Another embodiment consistent with the present disclosure may include aflexible electronics housing 1802. FIGS. 8 a-8 f illustrates anembodiment including a flexible electronics housing 1802. Utilizingflexible electronics housing 1802 may provide benefits with respect tothe size and shape of the electronics housing component. An electronicshousing must be large enough to accommodate the various componentscontained inside, such as electronic circuitry and a battery. It may bebeneficial to house the necessary components in a flexible electronicshousing 1802 with increased lateral dimensions and decreased verticaldimensions, in order to create a more comfortable experience for a user.A lower profile flexible electronics housing 1802 may also be lesslikely to catch its edges on bedclothes during a sleeping period.Additionally, when increasing lateral dimensions, it may be beneficialfor the housing to be flexible, so as to better conform to the bodycontour of the wearer. Flexible electronics housing 1802 may be achievedthrough the use of flexible components, such as a flexible circuit board1803 accommodating processor 144. Flexible electronics housing 1802 maybe between 10 and 50 mm in height, and may be at least three times widerin a lateral dimension than in a height dimension. In one embodiment,flexible electronics housing 1802 may be elliptical in shape, 14 mm highand having elliptical diameters of 40 mm and 50 mm.

Flexible electronics housing 1802 may further include all of the samefunctionality and components as described above with respect toelectronics housing 1202, for example, battery 1804, electricalconnectors 1805 (not shown), and recess 1806. Flexible electronicshousing 1802 may also be configured to contain a primary antenna. Recess1806 may be a connection portion configured to engage with a non-pouchconnector 1203 of carrier 1201. Some embodiments may include a pluralityof recesses 1806, for example, two or four recesses located near edgesof the housing, as shown in FIG. 8 b, or a centrally located recess anda plurality of recess located near edges of the housing, as shown inFIG. 8 c. The flexibility of flexible electronics housing 1802 maypermit the housing to better conform to the contours of a patient's bodywhen secured via connector 1203 and carrier 1201. Flexible electronicshousing 1802 may include a rigid portion 1807 in the center in whichelectrical connectors 1805 are located. Rigid portion 1807 may besubstantially inflexible. Rigid portion 1807 may ensure that electricalconnectors 1805 maintain contact with exposed electrical contactportions 1108 of carrier 1201. Rigid portion 1807 may also accommodate arigid battery 1804, or any other component in the housing required to berigid. In some embodiments, battery 1804 may provide the structure thatensures the rigidity of rigid portion 1807. Any combination of thecomponents within flexible housing 1802 may be flexible and/or rigid asrequired.

It is not necessary for flexible electronics housing 1802 to maintaincontact with carrier 1201 in portions away from electrical connectors1805 and exposed electrical contact portions 1108. For example, ifcarrier 1201 is contoured to a body of a subject, and bends away fromflexible electronics housing 1802, electrical communication may bemaintained through rigid portion 1807, as illustrated, for example, inFIG. 8 e. In some embodiments, each end of flexible housing 1802 may beconfigured to flex as much as sixty degrees away from a flat plane. Inembodiments that include rigid portion 1807, bending may begin at aportion immediately outside of rigid portion 1807. FIG. 8 f illustratesa flexible housing 1802 including a rigid portion 1807 with flexed endsbent at an angle α.

Flexible housing 1802 may be constructed of any suitable flexiblematerial, such as, for example, silicone, PMMA, PEEK, polypropylene, andpolystyrene. Flexible housing 1802 may be constructed from a top portionand a bottom portion, with the components being placed inside prior tosealing the top portion to the bottom portion. Flexible housing 1802 mayalso be constructed through overmolding techniques, wherein a flexiblematerial is molded over and around the required interior components.Flexible housing 1802 may be manufactured with additives, for example toinclude particulate substances to provide color or ferrite substances,which may reflect and/or absorb a radiofrequency signal produced by aprimary antenna contained within flexible housing 1802. A ferriteadditive 1843 in flexible housing 1802 may increase the efficiency ofthe primary antenna and/or may reduce excess external transmissions byreflecting and/or absorbing the radiofrequency signal.

In some embodiments consistent with the present disclosure, electricalcommunication between carrier 1201 and an electronics housing may bemade through electrical contacts 1810 located on a protruding non-pouchconnector 1811, as illustrated in FIG. 8 d. Electrical contacts 1810 maybe disposed circumferentially on non-pouch connector 1811 and located atdifferent heights. In such an embodiment, a connection portion of theelectronics housing may be configured to receive electrical contactsconfigured in this fashion.

In many of the examples described above, external unit 120 includes anelectronics housing and an adhesive carrier to which the housing may bereleasably connected. The examples provided are intended to be exemplaryonly, and are not intended to limit the placement or location of any ofthe components described. Additional embodiments including the locationof various components on either the housing or the carrier may berealized without departing from the scope of the invention. For example,in some embodiments, some or all of the required circuit component maybe printed on the carrier. In some embodiments, the primary antenna maybe contained within the housing. In some embodiments, a flexiblebattery, such as a paper battery, may be included on the carrier toreplace or supplement a battery contained in the housing.

In some embodiments, external control unit 120 may be configured forremote monitoring and control. In such an embodiment, electronicshousing 1202 may include, in addition to any or all of the elementsdiscussed above, a communications interface 145, and memory unit 143.Communications interface 145 may include a transceiver, configured forboth transmitting and receiving, a transmitter-receiver, a transmitteralone, and a receiver alone. Processor 144 may be configured to utilizecommunications interface 145 to communicate with a location remote fromthe control unit to transmit and/or receive information which may beretrieved from and/or stored in memory unit 143.

Processor 144 may be configured to cause application of a control signalto primary antenna 150. Processor 144 may further be configured tomonitor a feedback signal indicative of a subject's breathing. Such afeedback signal may include a coupled feedback signal developed on theprimary antenna 150 through wireless interaction with the secondaryantenna 152. Further details regarding the coupled feedback signal areprovided below. Processor 144 may then store information associated withor about both the control signal and the coupled feedback signal in thememory, and may utilize the communications interface 145 to transmit thestored information to a remote location. Processor 144 may also storeinformation about the external unit, for example, information aboutbattery depletion and energy expenditure. Processor 144 may also beconfigured to transmit collected information about the control signal,the feedback signal, and/or the external unit without first putting theinformation into storage. In such an embodiment, processor 144 may causetransmission of collected information via the communications interface145 as that information is received. Thus, in some embodiments, externalunit 120 may not require a memory.

In some embodiments, processor 144 may be configured to monitor afeedback signal provided by alternative means, such as electromyographyelectrodes, thermistors, accelerometers, microphones, piezoelectricsensors, etc., as previously described. Each of these means may providea feedback signal that may be indicative of a subject's breathing. Athermistor, for example, may provide a signal that relates to atemperature of a subject's expired air, inspired air, or a subject'sskin, which may be indicative of breathing. Electromyography electrodesmay provide a feedback signal indicative of breathing based on thedetection of muscle contractions. An accelerometer may provide a signalindicative of breathing by measuring a speed or rate at which parts ofthe subject's body, such as a chest or chin, moves. Microphones may beused to provide feedback signals, for example, by detecting acousticvariations coincident with a breathing pattern. Finally, piezoelectricsensors, for example, may be used to measure muscle movement.

The information associated with or about the control signal and thefeedback signal may include information about a patient's therapy.Information about the control signal may include a complete historyand/or any portion thereof of control signal transmissions caused by theprocessor. Information about the feedback signal may include a completehistory and/or any portion thereof of feedback signals measured, such asa history of coupled feedback signals developed on primary antenna 150.Information associated with the feedback signal may include informationabout a usage period of the control unit, energy expenditure of thecontrol unit, tongue movement, sleep disordered breathing occurrence,e.g. the occurrence of sleep apnea, hypopnea, and/or snoring, batterydepletion of the control unit, and information about tongue movement inresponse to the modulation signal. Together, the collected informationmay represent a complete history of a patient's therapy session. Thecontrol signal information and feedback signal information may be storedin a synchronized fashion, to ensure that subsequent data processing candetermine which portions of each signal occurred at the same time. A fewexamples of information that may be contained in control signal andfeedback signal information are described below. As noted above,however, the memory may store complete information about control signaltransmissions and feedback signals. Thus, the storage and/ortransmission of any portion of these signals or any data describing themis also contemplated.

In some embodiments, information about the control signal may includesummarizing information, for example a number of times or frequency withwhich the control signal was utilized to induce nerve modulation.Information about the control signal may include strength, duration, andother descriptive parameters of the control signal, at both modulationand sub-modulation levels. The information transmitted and receivedduring communication with the remote location may include informationabout a coupled feedback signal. Information about the feedback signalmay include information indicative of a patient's tongue movement ormotion and information indicative of a frequency or duration of sleepdisordered breathing events. In some embodiments, the stored informationmay be information that combines control signal information and feedbacksignal information, for example, information that describes a patientresponse to nerve modulation signals.

The stored information may be transmitted to a location remote fromcontrol unit 120 via a communications interface 145. Communicationsinterface 145 may include a transceiver configured to send and receiveinformation. The transceiver may utilize various transmission methodsknown in the art, for example wi-fi, Bluetooth, radio, RFID, smart chipor other near field communication device, and any other method capableof wirelessly transmitting information. Communications interface 145 ortransceiver may also be configured to transmit the stored informationthrough a wired electrical connection. The transmitted information maybe received by a remote location. A remote location suitable for receiptof the transmitted information may function as a relay station, or maybe a final destination. A final destination, for example, may include acentralized server location. External unit 120 may transmit the storedinformation to a relay station device which may then transmit theinformation to another relay station device or final destination. Forexample, a relay station device may include a patient's mobile device,smartphone, home computer, and/or a dedicated relay unit. A dedicatedrelay unit may include an antenna situated beneath a patient's pillow,for example to permit the transmission of a signal across a signal incircumstances where communications interface 145 may not be powerfulenough or large enough to transmit a signal more than a few inches orfeet. In some embodiments, a dedicated relay unit may also include amedical device console, described in greater detail below with respectto FIG. 9, configured to receive information transmitted bycommunications interface 145. The relay station device may receive thetransmitted information and may store it prior to transmitting it, via,for example, any known communication technique, to a final destination.For example, the relay station may receive information from the externalunit on a nightly basis, but only establish a connection with a finaldestination on a weekly basis. The relay station may also performanalysis on the received information prior to establishing a connectionwith a final destination. In some embodiments, a relay station devicemay relay received information immediately as it is received, or as soonas connection with the final destination can be established.

In some embodiments, external control unit 120 may be programmable andreprogrammable. For example, as described above, a memory included withexternal control unit 120 may store information associated with or aboutthe control signal and the coupled feedback signal and may includeinformation about therapy a patient has undergone. Further, a memoryincluded with an external control unit 120 may be a programmable and/orreprogrammable memory configured to store information associated with atleast one characteristic of sleep disordered breathing exhibited by asubject. Processor 144 may utilize the information associated with atleast one characteristic of sleep disordered breathing to generate ahypoglossal nerve modulation control signal based on the information.That is, processor 144 may determine modulation parameters based oninformation about a patient's sleep disordered breathingcharacteristics. In some embodiments, such information may be determinedby physicians, for example through the use of sleep lab equipment suchas EKGs, EEGs, EMGs, breathing monitors, blood oxygen monitors,temperature monitors, brain activity monitors, cameras, accelerometers,electromyography equipment, and any other equipment useful formonitoring the sleep of a patient, and programmed into the memory. Insome embodiments, such information may be determined by processor 144 bymonitoring of the control signal and the coupled feedback signal.

As described above, external control unit 120 may include componentsthat permit the recording, storage, reception, and transmission ofinformation about a patient's sleep breathing patterns, about anytherapy administered to the patient during sleep, and about the responseof a patient's sleep breathing patterns to administered therapy. Suchinformation may be stored for later transmission, may be transmitted asit is received or shortly thereafter, may be received and stored forlater use, and/or may be utilized by processor 144 as it is received orshortly thereafter. This information may be generated by processor 144through monitoring of a control signal transmitted to an implant unit110 and a coupled feedback signal received therefrom and/or throughother means described herein for processor 144 to collect feedback, suchas electromyography electrodes, piezoelectric sensors, audio sensors,thermistors, and accelerometers. This information may also be generatedthrough various equipment at the disposal of physicians in, for example,a sleep lab. This stored information may be utilized, for example byprocessor 144 or by software running on a standard computer, todetermine parameters of a hypoglossal nerve modulation control signalspecific to a certain patient, based on the collected information. In anembodiment where parameters are determined by outside of externalcontrol unit 120, such parameters may be received by communicationsinterface 145 of external control unit 120 as described above. Someexamples describing the use of these capabilities is included below.

In an embodiment for determining initial modulation parameters for apatient, the above described system may operate as follows. Afterundergoing a surgical procedure to receive an implant unit 110, apatient may visit a sleep lab to determine initial modulation controlsignal parameters, such as pulse frequency, amplitude, train length,etc. Modulation control signal parameters may include pulse trainparameters, described in greater detail below with respect to FIG. 17. Aphysician may use an endoscope to inspect an awake patient's airwayduring hypoglossal nerve modulation to determine that implant unit 110is able to effectively cause airway dilation. Then, the patient may goto sleep in the sleep lab while being monitored by the physician. Thepatient's sleep may be monitored through a variety of tools available ina sleep lab, such as EKGs, EEGs, EMGs, breathing monitors, blood oxygenmonitors, temperature monitors, brain activity monitors, cameras,electromyography electrodes, and any other equipment useful formonitoring the sleep of a patient. The monitoring equipment may be usedto determine a patient's quality of sleep and to determine the onset ofsleep disordered breathing. The physician may also monitor the patient'ssleep through the use of external unit 120. Through a wireless or wiredcommunication set up through communications interface 145 with processor144, the physician may also monitor information gathered by externalunit 120, e.g. modulation and sub-modulation control signals, feedbacksignals, battery levels, etc. Through communications interface 145, thephysician may also control the modulation and sub-modulation signalsgenerated by processor 144.

Thus, a physician may, through information gathered by sleep labequipment and external unit 120, monitor a patient's sleep breathingpatterns, including instances of sleep disordered breathing, and, inresponse to the monitored information, update the programming ofprocessor 144 to optimize the therapy delivered to the patient in orderto reduce instances of sleep disordered breathing. That is, processor144 may be programmed to use a control signal that is tailored to causeoptimum modulation, based on any or all of the information collected. Inembodiments involving the application of a continuous modulation pulsetrain, such optimization may include selecting parameters, such as thefrequency, amplitude, and duration of modulation pulses. For example, aphysician observing a high frequency of sleep disordered breathingoccurrences may adjust the parameters of a modulation pulse train untilthe sleep disordered breathing occurrences are reduced in number or stopaltogether. The physician, thus, may be able to program processor 144 toeffectively modulate the hypoglossal nerve to stop or minimize sleepdisordered breathing without stimulating any more than necessary.

In some embodiments, the modulation pulse train may not be programmedwith constant parameter values, but may be programmed to change duringthe course of an evening, or therapy period. Constant modulationsignals, whether they are constant in amplitude, duration, and/orfrequency of modulation pulses may result in diminishing sensitivity orresponse to modulation signals over time. For example, muscularcontractions in response to a constant modulation signal may be reducedover time. Over the course of a therapy period, the muscularcontractions resulting from a steady pulse train may be diminished,which may, in turn, cause an increase in sleep disordered breathingevents. In order to counteract this effect, a pulse train may bedynamically modified during a therapy period via a plurality ofpredetermined alterations to the pulse train of a modulation controlsignal. For example, processor 144 may be programmed to alter at leastone characteristic of the modulation pulse train, e.g., to increase,decrease, or otherwise alter the amplitude, duration and/or frequency ofmodulation pulses over the course of a therapy period. Any and allcharacteristics of a pulse train of a modulation control signal may bealtered over the course of therapy period to increase modulationefficacy. As described above, physician monitored therapy periods may beutilized to determine an optimal pattern of alterations to themodulation control signal.

In embodiments involving selective modulation based on the detection ofsleep disordered breathing precursors, such optimization may includeselecting not only modulation parameters, which may be selected so as tovary with time over the course of a therapy period, but also feedbackparameters and thresholds consistent with a sleep disordered breathingdetermination. For example, a physician may compare indications oftongue movement collected by external unit 120 with extrinsic indicatorsof sleep disordered breathing from sleep lab equipment. The physicianmay then correlate observed sleep disordered breathing patterns withdetect tongue movement patterns, and program processor 144 to generate amodulation control signal when those tongue movement patterns aredetected.

In some embodiments, the actions of the physician as described above maybe performed by on a computer running software dedicated to the task. Acomputer system may be programmed to monitor the sleep breathingpatterns of a patient and to program, reprogram, and/or update theprogramming of processor 144 accordingly.

The present disclosure contemplates several additional embodiments forthe updating of modulation parameters. In one embodiment, a patient,utilizing the sleep disordered breathing therapy system at home, mayhave their equipment updated based on nightly data collection. Asdescribed above, communications interface 145 of external unit 120 maytransmit information either to a relay station or directly to a finaldestination on a regular basis, monthly, weekly, daily, and even hourlyor constantly. In some embodiments, the communications interface 145 ofexternal unit 120 may be configured to transmit information based oncertain thresholds, for example, if a number of sleep disorderedbreathing occurrences exceeds a predetermined number. At the finaldestination, which may be a remote location, e.g. a physician's office,or console device in the patient's home, the collected information maybe analyzed in any of the ways described above and used to determine newmodulation parameters, to be transmitted, via the communicationsinterface 145, back to the patient's external unit 120. Thus, thepatient's sleep may be monitored on a regular basis, either throughautomated software or with the aid of a physician, and the patient'stherapy may be updated accordingly.

In some embodiments, the information may be transferred to a relaystation device or to a final destination when the patient placesexternal unit 120 in a charging device.

For example, a medical console device, illustrated in FIG. 9, may beprovided with an electrical interface 955 configured to receive therapyinformation from a patient's external unit 120. Medical console device950 may further include a data storage unit 956 for storing the therapyinformation and at least one processing device 957 for analyzing thetherapy information and determining updated control parameters forexternal unit 120. Medical console device 950 may transmit updatedcontrol parameters to communications interface 145 of external unit 120via electrical interface 955. Such communication may be wired, or may bewireless transmission through any known means, such as wi-fi, bluetooth,RFID, etc. The information may then be processed by the console, ortransmitted to a final destination for processing. Transmission to afinal destination may be accomplished, for example, via the internet,wireless connection, cellular connection, or any other suitabletransmission means. The information may be used to determine updatedmodulation parameters for processor 144, either by the medical consoledevice 950 or by a different final destination. In some embodiments,external unit 120 may be disposable. In such embodiments, processor 144may be programmed with a patient's particular therapy regime throughconnection, wireless or wired, to the medical console device 950 priorto therapy. In some embodiments, a medical console device may beconfigured to transmit modulation parameters to several disposableexternal units 120 at the same time. In some embodiments, external unit120 may be recharged via electrical interface 955, in either a wired orwireless fashion. In some embodiments, medical console device 950 may beconfigured for bedside use, and may include, for example, all of thefunctions of a standard alarm clock/radio.

In some embodiments, information collected and transmitted by externalcontrol unit 120 may be used to monitor patient compliance. For example,by monitoring information such as battery depletion, modulationfrequency, and any other parameter discussed herein, a physician may beable to determine whether or not a patient is complying with a therapyregime. Physicians may use this information to follow up with patient'sand alter therapy regimes if necessary. In some embodiments, informationcollected and transmitted by external control unit 120 may be used tomonitor system efficacy. For example, it may be difficult for a patientto determine how successful therapy is, as they sleep during therapyperiods. The equipment and components described herein may be used toprovide information to a patient and/or their physician about theeffectiveness of treatment. Such information may also be used todetermine effectiveness of the implant unit 110 specifically. Forexample, if levels of nightly battery depletion increase without acorresponding increase in the frequency of modulation, it may beindicative of a problem with implant unit 110 or its implantation.

Implant unit 110 may additionally include a plurality offield-generating implant electrodes 158 a, 158 b. The electrodes mayinclude any suitable shape and/or orientation on the implant unit solong as the electrodes may be configured to generate an electric fieldin the body of a patient. Implant electrodes 158 a and 158 b may alsoinclude any suitable conductive material (e.g., copper, silver, gold,platinum, iridium, platinum-iridium, platinum-gold, conductive polymers,etc.) or combinations of conductive (and/or noble metals) materials. Insome embodiments, for example, the electrodes may include short lineelectrodes, circular electrodes, and/or circular pairs of electrodes. Asshown in FIG. 10, electrodes 158 a and 158 b may be located on an end ofa first extension 162 a of an elongate arm 162. The electrodes, however,may be located on any portion of implant unit 110. Additionally, implantunit 110 may include electrodes located at a plurality of locations, forexample on an end of both a first extension 162 a and a second extension162 b of elongate arm 162, as illustrated, for example, in FIG. 11 a.Positioning electrodes on two extensions of elongate arm 162 may permitbilateral hypoglossal nerve stimulation, as discussed further below.Implant electrodes may have a thickness between about 200 nanometers and1 millimeter. Anode and cathode electrode pairs may be spaced apart byabout a distance of about 0.2 mm to 25 mm. In additional embodiments,anode and cathode electrode pairs may be spaced apart by a distance ofabout 1 mm to 10 mm, or between 4 mm and 7 mm. Adjacent anodes oradjacent cathodes may be spaced apart by distances as small as 0.001 mmor less, or as great as 25 mm or more. In some embodiments, adjacentanodes or adjacent cathodes may be spaced apart by a distance betweenabout 0.2 mm and 1 mm.

FIG. 10 provides a schematic representation of an exemplaryconfiguration of implant unit 110. As illustrated in FIG. 10, in oneembodiment, the field-generating electrodes 158 a and 158 b may includetwo sets of four circular electrodes, provided on flexible carrier 161,with one set of electrodes providing an anode and the other set ofelectrodes providing a cathode. Implant unit 110 may include one or morestructural elements to facilitate implantation of implant unit 110 intothe body of a patient. Such elements may include, for example, elongatedarms, suture holes, polymeric surgical mesh, biological glue, spikes offlexible carrier protruding to anchor to the tissue, spikes ofadditional biocompatible material for the same purpose, etc. thatfacilitate alignment of implant unit 110 in a desired orientation withina patient's body and provide attachment points for securing implant unit110 within a body. For example, in some embodiments, implant unit 110may include an elongate arm 162 having a first extension 162 a and,optionally, a second extension 162 b. Extensions 162 a and 162 b may aidin orienting implant unit 110 with respect to a particular muscle (e.g.,the genioglossus muscle), a nerve within a patient's body, or a surfacewithin a body above a nerve. For example, first and second extensions162 a, 162 b may be configured to enable the implant unit to conform atleast partially around soft or hard tissue (e.g., nerve, bone, ormuscle, etc.) beneath a patient's skin. Further, implant unit 110 mayalso include one or more suture holes 160 located anywhere on flexiblecarrier 161. For example, in some embodiments, suture holes 160 may beplaced on second extension 162 b of elongate arm 162 and/or on firstextension 162 a of elongate arm 162. Implant unit 110 may be constructedin various shapes. Additionally, or alternatively, implant unit 110 mayinclude surgical mesh 1050 or other perforatable material, described ingreater detail below with respect to FIG. 12. In some embodiments,implant unit may appear substantially as illustrated in FIG. 10. Inother embodiments, implant unit 110 may lack illustrated structures suchas second extension 162 b, or may have additional or differentstructures in different orientations. Additionally, implant unit 110 maybe formed with a generally triangular, circular, or rectangular shape,as an alternative to the winged shape shown in FIG. 10. In someembodiments, the shape of implant unit 110 (e.g., as shown in FIG. 10)may facilitate orientation of implant unit 110 with respect to aparticular nerve to be modulated. Thus, other regular or irregularshapes may be adopted in order to facilitate implantation in differingparts of the body.

As illustrated in FIG. 10, secondary antenna 152 and electrodes 158 a,158 b may be mounted on or integrated with flexible carrier 161. Variouscircuit components and connecting wires may be used to connect secondaryantenna with implant electrodes 158 a and 158 b. To protect the antenna,electrodes, and implantable circuit components from the environmentwithin a patient's body, implant unit 110 may include a protectivecoating that encapsulates implant unit 110. In some embodiments, theprotective coating may be made from a flexible material to enablebending along with flexible carrier 161. The encapsulation material ofthe protective coating may also resist humidity penetration and protectagainst corrosion. In some embodiments, the protective coating mayinclude a plurality of layers, including different materials orcombinations of materials in different layers.

In some embodiments of the present disclosure, the encapsulationstructure of implanted unit may include two layers. For example, a firstlayer may be disposed over at least a portion of the implantable circuitarranged on the substrate, and a second layer may be disposed over thefirst layer. In some embodiments, the first layer may be disposeddirectly over the implantable circuit, but in other embodiments, thefirst layer may be disposed over an intervening material between thefirst layer and the implantable circuit. In some embodiments, the firstlayer may provide a moisture barrier and the second layer may provide amechanical protection (e.g., at least some protection from physicaldamage that may be caused by scratching, impacts, bending, etc.) for theimplant unit. The terms “encapsulation” and “encapsulate” as used hereinmay refer to complete or partial covering of a component. In someembodiments component may refer to a substrate, implantable circuit,antenna, electrodes, any parts thereof, etc. The term “layer” as usedherein may refer to a thickness of material covering a surface orforming an overlying part or segment. The layer thickness can bedifferent from layer to layer and may depend on the covering materialand the method of forming the layer. For example, a layer disposed bychemical vapor may be thinner than a layer disposed through othermethods.

Other configurations may also be employed. For example, another moisturebarrier may be formed over the outer mechanical protection layer. Insuch embodiments, a first moisture barrier layer (e.g., parylene) may bedisposed over (e.g., directly over or with intervening layers) theimplantable circuit, a mechanical protection layer (e.g., silicone) maybe formed over the first moisture barrier, and second moisture barrier(e.g., parylene) may be disposed over the mechanical protection layer.

FIG. 11 a is a perspective view of an alternate embodiment of an implantunit 110, according to an exemplary embodiment of the presentdisclosure. As illustrated in FIG. 11 a, implant unit 110 may include aplurality of electrodes, located, for example, at the ends of firstextension 162 a and second extension 162 b. FIG. 11 a illustrates anembodiment wherein implant electrodes 158 a and 158 b include short lineelectrodes.

FIG. 11 b illustrates another alternate embodiment of implant unit 810,according to an exemplary embodiment of the present disclosure. Implantunit 810 is configured such that circuitry 880 is located in a verticalarrangement with secondary antenna 852. Implant unit 810 may includefirst extension 162 a and second extension 162 b, wherein one or both ofthe extensions accommodate electrodes 158 a and 158 b.

FIG. 12 illustrates another exemplary embodiment of encapsulated implantunit 110. Exemplary embodiments may incorporate some or all of thefeatures illustrated in FIG. 10 as well as additional features. Aprotective coating of implant unit 110 may include a primary capsule1021. Primary capsule 1021 may encapsulate the implant unit 110 and mayprovide mechanical protection for the implant unit 110. For example, thecomponents of implant unit 110 may be delicate, and the need to handlethe implant unit 110 prior to implantation may require additionalprotection for the components of implant unit 110, and primary capsule1021 may provide such protection. Primary capsule 1021 may encapsulateall or some of the components of implant unit 110. For example, primarycapsule 1021 may encapsulate antenna 152, flexible carrier 161, andimplantable circuit 180. The primary capsule may leave part or all ofelectrodes 158 a, 158 b exposed enabling them to deliver energy formodulating a nerve unimpeded by material of the primary capsule. Inalternative embodiments, different combinations of components may beencapsulated or exposed.

Primary capsule 1021 may be fashioned of a material and thickness suchthat implant unit 110 remains flexible after encapsulation. Primarycapsule 1021 may include any suitable bio-compatible material, such assilicone, or polyimides, phenyltrimethoxysilane (PTMS), polymethylmethacrylate (PMMA), Parylene C, liquid polyimide, laminated polyimide,polyimide, Kapton, black epoxy, polyether ketone (PEEK), Liquid CrystalPolymer (LCP), or any other suitable biocompatible coating.

In some embodiments, all or some of the circuitry components included inimplant 110 may be housed in a rigid housing, as illustrated in FIGS. 13a-b. Rigid housing 1305 may provide the components of implant 110 withadditional mechanical and environmental protections. A rigid housing mayprotect the components of implant 110 from physical trauma duringimplantation or from physical trauma caused by the tissue movement at animplantation site. Rigid housing may also provide additionalenvironmental protections from the corrosive environment within thebody. Furthermore, the use of a rigid housing may simplify a process formanufacturing implant unit 110.

FIG. 13 illustrates an embodiment including an implant unit 110 with arigid housing. As shown in FIG. 13, implant unit 110 may include all ofthe components of implant unit 110, e.g. modulation electrodes 158 a,158 b, secondary antenna 152, flexible carrier 161, extension arms 162a, 162 b, as well as circuitry 180 and any other component describedherein. Some, or all, of these components, e.g. circuitry 180, may beincluded inside rigid housing 1305.

Rigid housing 130 may be constructed, for example, of ceramic, glass,and/or titanium, and may include a ceramic clamshell. Rigid housing 130may, for example be welded closed with a biocompatible metal such asgold or titanium, or closed with any other suitable methods. Such ahousing may also include a ceramic bottom portion 1306 and a titanium orceramic upper portion 1307. Rigid housing 1305 may include one or moreconductive feedthroughs 1308 to make contact with circuitry on flexiblecarrier 161. Inside the housing, conductive feedthroughs 1308 may besoldered, welded, or glued to circuitry 180, or any other internalcomponent, through traditional soldering techniques. Conductivefeedthroughs 1308 may comprise gold, platinum, or any other suitableconductive material. In one embodiment, rigid housing 1305 may includefour feedthroughs 1308 comprising positive and negative connections forthe modulation electrodes 158 a, 158 b, and the secondary antenna 152.Of course, any suitable number of feedthroughs 1308 may be provided.

Rigid housing 1308 may be mounted to flexible carrier 161 throughcontrolled collapse chip connection, or C4 manufacturing. Using thistechnique, external portions 1309 of each conductive feedthrough 1308,which extend beyond the surface of rigid housing 1308, may be alignedwith solder bumps on flexible carrier 161. Solder bumps may, in turn,connected to the electrical traces of flexible carrier 161. Oncealigned, the solder is caused to reflow, creating an electricalconnection between the electrical traces of flexible carrier 161 and theinternal components of rigid housing 1305 via feedthroughs 1308. Oncethe electrical connection has been made, a non-conductive, orinsulative, adhesive 1310 may be used to fill the gaps between the rigidhousing and the flexible carrier in and around the soldered connections.The insulative adhesive 1310 may provide both mechanical protection toensure that rigid housing 1305 does not separate from flexible carrier161, as well as electrical protection to ensure that the feedthroughs1308 do not short to each other.

Once mounted to flexible carrier 161, rigid housing 1305 and flexiblecarrier 161 may be encapsulated together via a multi-layer encapsulationstructure described above.

Returning now to FIG. 12, also illustrated is encapsulated surgical mesh1050. Surgical mesh 1050 may provide a larger target area for surgeonsto use when suturing implant unit 110 into place during implantation.The entire surgical mesh 1050 may be encapsulated by primary capsule1021, permitting a surgeon to pass a needle through any portion of themesh without compromising the integrity of implant unit 110. Surgicalmesh 1050 may additionally be used to cover suture holes 160, permittinglarger suture holes 160 that may provide surgeons with a greater targetarea. Surgical mesh 1050 may also encourage surrounding tissue to bondwith implant unit 110. In some embodiments, a surgeon may pass asurgical suture needle through suture holes 160, located on oneextension 162 a of an elongate arm 162 of implant unit 110, throughtissue of the subject, and through surgical mesh 1050 provided on asecond extension 162 b of elongate arm 162 of implant unit 110. In thisembodiment, the larger target area provided by surgical mesh 1050 mayfacilitate the suturing process because it may be more difficult toprecisely locate a suture needle after passing it through tissue.Implantation and suturing procedures may be further facilitated throughthe use of a delivery tool, described in greater detail below.

Returning to FIGS. 2 and 3, external unit 120 may be configured tocommunicate with implant unit 110. For example, in some embodiments, aprimary signal may be generated on primary antenna 150, using, e.g.,processor 144, signal source 142, and amplifier 146. More specifically,in one embodiment, power source 140 may be configured to provide powerto one or both of the processor 144 and the signal source 142. Theprocessor 144 may be configured to cause signal source 142 to generate asignal (e.g., an RF energy signal). Signal source 142 may be configuredto output the generated signal to amplifier 146, which may amplify thesignal generated by signal source 142. The amount of amplification and,therefore, the amplitude of the signal may be controlled, for example,by processor 144. The amount of gain or amplification that processor 144causes amplifier 146 to apply to the signal may depend on a variety offactors, including, but not limited to, the shape, size, and/orconfiguration of primary antenna 150, the size of the patient, thelocation of implant unit 110 in the patient, the shape, size, and/orconfiguration of secondary antenna 152, a degree of coupling betweenprimary antenna 150 and secondary antenna 152 (discussed further below),a desired magnitude of electric field to be generated by implantelectrodes 158 a, 158 b, etc. Amplifier 146 may output the amplifiedsignal to primary antenna 150.

External unit 120 may communicate a primary signal on primary antenna tothe secondary antenna 152 of implant unit 110. This communication mayresult from coupling between primary antenna 150 and secondary antenna152. Such coupling of the primary antenna and the secondary antenna mayinclude any interaction between the primary antenna and the secondaryantenna that causes a signal on the secondary antenna in response to asignal applied to the primary antenna. In some embodiments, couplingbetween the primary and secondary antennas may include capacitivecoupling, inductive coupling, radiofrequency coupling, etc. and anycombinations thereof.

Coupling between primary antenna 150 and secondary antenna 152 maydepend on the proximity of the primary antenna relative to the secondaryantenna. That is, in some embodiments, an efficiency or degree ofcoupling between primary antenna 150 and secondary antenna 152 maydepend on the proximity of the primary antenna to the secondary antenna.The proximity of the primary and secondary antennas may be expressed interms of a coaxial offset (e.g., a distance between the primary andsecondary antennas when central axes of the primary and secondaryantennas are co-aligned), a lateral offset (e.g., a distance between acentral axis of the primary antenna and a central axis of the secondaryantenna), and/or an angular offset (e.g., an angular difference betweenthe central axes of the primary and secondary antennas). In someembodiments, a theoretical maximum efficiency of coupling may existbetween primary antenna 150 and secondary antenna 152 when both thecoaxial offset, the lateral offset, and the angular offset are zero.Increasing any of the coaxial offset, the lateral offset, and theangular offset may have the effect of reducing the efficiency or degreeof coupling between primary antenna 150 and secondary antenna 152.

As a result of coupling between primary antenna 150 and secondaryantenna 152, a secondary signal may arise on secondary antenna 152 whenthe primary signal is present on the primary antenna 150. Such couplingmay include inductive/magnetic coupling, RF coupling/transmission,capacitive coupling, or any other mechanism where a secondary signal maybe generated on secondary antenna 152 in response to a primary signalgenerated on primary antenna 150. Coupling may refer to any interactionbetween the primary and secondary antennas. In addition to the couplingbetween primary antenna 150 and secondary antenna 152, circuitcomponents associated with implant unit 110 may also affect thesecondary signal on secondary antenna 152. Thus, the secondary signal onsecondary antenna 152 may refer to any and all signals and signalcomponents present on secondary antenna 152 regardless of the source.

While the presence of a primary signal on primary antenna 150 may causeor induce a secondary signal on secondary antenna 152, the couplingbetween the two antennas may also lead to a coupled signal or signalcomponents on the primary antenna 150 as a result of the secondarysignal present on secondary antenna 152. A signal on primary antenna 150induced by a secondary signal on secondary antenna 152 may be referredto as a primary coupled signal component. The primary signal may referto any and all signals or signal components present on primary antenna150, regardless of source, and the primary coupled signal component mayrefer to any signal or signal component arising on the primary antennaas a result of coupling with signals present on secondary antenna 152.Thus, in some embodiments, the primary coupled signal component maycontribute to the primary signal on primary antenna 150.

Implant unit 110 may be configured to respond to external unit 120. Forexample, in some embodiments, a primary signal generated on primary coil150 may cause a secondary signal on secondary antenna 152, which inturn, may cause one or more responses by implant unit 110. In someembodiments, the response of implant unit 110 may include the generationof an electric field between implant electrodes 158 a and 158 b.

FIG. 14 illustrates circuitry 170 that may be included in external unit120 and circuitry 180 that may be included in implant unit 110.Additional, different, or fewer circuit components may be included ineither or both of circuitry 170 and circuitry 180. As shown in FIG. 14,secondary antenna 152 may be arranged in electrical communication withimplant electrodes 158 a, 158 b. In some embodiments, circuitryconnecting secondary antenna 152 with implant electrodes 158 a and 158 bmay cause a voltage potential across implant electrodes 158 a and 158 bin the presence of a secondary signal on secondary antenna 152. Thisvoltage potential may be referred to as a field inducing signal, as thisvoltage potential may generate an electric field between implantelectrodes 158 a and 158 b. More broadly, the field inducing signal mayinclude any signal (e.g., voltage potential) applied to electrodesassociated with the implant unit that may result in an electric fieldbeing generated between the electrodes.

The field inducing signal may be generated as a result of conditioningof the secondary signal by circuitry 180. As shown in FIG. 6, circuitry170 of external unit 120 may be configured to generate an AC primarysignal on primary antenna 150 that may cause an AC secondary signal onsecondary antenna 152. In certain embodiments, however, it may beadvantageous (e.g., in order to generate a unidirectional electric fieldfor modulation of a nerve) to provide a DC field inducing signal atimplant electrodes 158 a and 158 b. To convert the AC secondary signalon secondary antenna 152 to a DC field inducing signal, circuitry 180 inimplant unit 110 may include an AC-DC converter. The AC to DC convertermay include any suitable converter known to those skilled in the art.For example, in some embodiments the AC-DC converter may includerectification circuit components including, for example, diode 156 andappropriate capacitors and resistors. In alternative embodiments,implant unit 110 may include an AC-AC converter, or no converter, inorder to provide an AC field inducing signal at implant electrodes 158 aand 158 b.

As noted above, the field inducing signal may be configured to generatean electric field between implant electrodes 158 a and 158 b. In someinstances, the magnitude and/or duration of the generated electric fieldresulting from the field inducing signal may be sufficient to modulateone or more nerves in the vicinity of electrodes 158 a and 158 b. Insuch cases, the field inducing signal may be referred to as a modulationsignal. In other instances, the magnitude and/or duration of the fieldinducing signal may generate an electric field that does not result innerve modulation. In such cases, the field inducing signal may bereferred to as a sub-modulation signal.

Various types of field inducing signals may constitute modulationsignals. For example, in some embodiments, a modulation signal mayinclude a moderate amplitude and moderate duration, while in otherembodiments, a modulation signal may include a higher amplitude and ashorter duration. Various amplitudes and/or durations of field-inducingsignals across electrodes 158 a, 158 b may result in modulation signals,and whether a field-inducing signal rises to the level of a modulationsignal can depend on many factors (e.g., distance from a particularnerve to be stimulated; whether the nerve is branched; orientation ofthe induced electric field with respect to the nerve; type of tissuepresent between the electrodes and the nerve; etc.).

In some embodiments, the electrodes 158 a and 158 b may generate anelectric field configured to penetrate intervening tissue 111 betweenthe electrodes and one or more nerves. The intervening tissue 111 mayinclude muscle tissue, bone, connective tissue, adipose tissue, organtissue, or any combination thereof. For subjects suffering withobstructive sleep apnea, for instance, the intervening tissue mayinclude the genioglossus muscle.

The generation of electric fields configured to penetrate interveningtissue is now discussed with respect to FIGS. 15 a, 15 b, 15 c, and 16.In response to a field inducing signal, implant electrodes 158 a and 158b may be configured to generate an electric field with field linesextending generally in the longitudinal direction of one or more nervesto be modulated. In some embodiments, implant electrodes 158 a and 158 bmay be spaced apart from one another along the longitudinal direction ofa nerve to facilitate generation of such an electric field. The electricfield may also be configured to extend in a direction substantiallyparallel to a longitudinal direction of at least some portion of thenerve to be modulated. For example, a substantially parallel field mayinclude field lines that extend more in a longitudinal direction than atransverse direction compared to the nerve. Orienting the electric fieldin this way may facilitate electrical current flow through a nerve ortissue, thereby increasing the likelihood of eliciting an actionpotential to induce modulation.

FIG. 15 a illustrates a pair of electrodes 158 a, 158 b spaced apartfrom one another along the longitudinal direction of nerve 210 tofacilitate generation of an electric field having field lines 220substantially parallel to the longitudinal direction of nerve 210. InFIG. 15 a, modulation electrodes 158 a, 158 b are illustrated as lineelectrodes, although the generation of substantially parallel electricfields may be accomplished through the use of other types of electrodes,for example, a series of point electrodes. Utilizing an electric fieldhaving field lines 220 extending in a longitudinal direction of nerve210 may serve to reduce the amount of energy required to achieve neuralmodulation.

Naturally functioning neurons function by transmitting action potentialsalong their length. Structurally, neurons include multiple ion channelsalong their length that serve to maintain a voltage potential gradientacross a plasma membrane between the interior and exterior of theneuron. Ion channels operate by maintaining an appropriate balancebetween positively charged sodium ions on one side of the plasmamembrane and negatively charged potassium ions on the other side of theplasma membrane. A sufficiently high voltage potential differencecreated near an ion channel may exceed a membrane threshold potential ofthe ion channel. The ion channel may then be induced to activate,pumping the sodium and potassium ions across the plasma membrane toswitch places in the vicinity of the activated ion channel. This, inturn, further alters the potential difference in the vicinity of the ionchannel, which may serve to activate a neighboring ion channel. Thecascading activation of adjacent ion channels may serve to propagate anaction potential along the length of the neuron. Further, the activationof an ion channel in an individual neuron may induce the activation ofion channels in neighboring neurons that, bundled together, form nervetissue. The activation of a single ion channel in a single neuron,however, may not be sufficient to induce the cascading activation ofneighboring ion channels necessary to permit the propagation of anaction potential. Thus, the more ion channels in a locality that may berecruited by an initial potential difference, caused through naturalmeans such as the action of nerve endings or through artificial means,such as the application of electric fields, the more likely thepropagation of an action potential may be. The process of artificiallyinducing the propagation of action potentials along the length of anerve may be referred to as stimulation, or up modulation.

Neurons may also be prevented from functioning naturally throughconstant or substantially constant application of a voltage potentialdifference. After activation, each ion channel experiences a refractoryperiod, during which it “resets” the sodium and potassium concentrationsacross the plasma membrane back to an initial state. Resetting thesodium and potassium concentrations causes the membrane thresholdpotential to return to an initial state. Until the ion channel restoresan appropriate concentration of sodium and potassium across the plasmamembrane, the membrane threshold potential will remain elevated, thusrequiring a higher voltage potential to cause activation of the ionchannel. If the membrane threshold potential is maintained at a highenough level, action potentials propagated by neighboring ion channelsmay not create a large enough voltage potential difference to surpassthe membrane threshold potential and activate the ion channel. Thus, bymaintaining a sufficient voltage potential difference in the vicinity ofa particular ion channel, that ion channel may serve to block furthersignal transmission. The membrane threshold potential may also be raisedwithout eliciting an initial activation of the ion channel. If an ionchannel (or a plurality of ion channels) are subjected to an elevatedvoltage potential difference that is not high enough to surpass themembrane threshold potential, it may serve to raise the membranethreshold potential over time, thus having a similar effect to an ionchannel that has not been permitted to properly restore ionconcentrations. Thus, an ion channel may be recruited as a block withoutactually causing an initial action potential to propagate. This methodmay be valuable, for example, in pain management, where the propagationof pain signals is undesired. As described above with respect tostimulation, the larger the number of ion channels in a locality thatmay be recruited to serve as blocks, the more likely the chance that anaction potential propagating along the length of the nerve will beblocked by the recruited ion channels, rather than traveling throughneighboring, unblocked channels.

The number of ion channels recruited by a voltage potential differencemay be increased in at least two ways. First, more ion channels may berecruited by utilizing a larger voltage potential difference in a localarea. Second, more ion channels may be recruited by expanding the areaaffected by the voltage potential difference.

Returning to FIG. 15 a, it can be seen that, due to the electric fieldlines 220 running in a direction substantially parallel to thelongitudinal direction of the nerve 210, a large portion of nerve 210may encounter the field. Thus, more ion channels from the neurons thatmake up nerve 210 may be recruited without using a larger voltagepotential difference. In this way, modulation of nerve 210 may beachieved with a lower current and less power usage. FIG. 15 billustrates an embodiment wherein electrodes 158 a and 158 are stillspaced apart from one another in a longitudinal direction of at least aportion of nerve 210. A significant portion of nerve 210 remains insideof the electric field. FIG. 15 c illustrates a situation whereinelectrodes 158 a and 158 b are spaced apart from one another in atransverse direction of nerve 210. In this illustration, it can be seenthat a significantly smaller portion of nerve 210 will be affected byelectric field lines 220.

FIG. 16 illustrates potential effects of electrode configuration on theshape of a generated electric field. The top row of electrodeconfigurations, e.g. A, B, and C, illustrates the effects on theelectric field shape when a distance between electrodes of a constantsize is adjusted. The bottom row of electrode configurations, e.g. D, E,and F illustrates the effects on the electric field shape when the sizeof electrodes of constant distance is adjusted.

In embodiments consistent with the present disclosure, modulationelectrodes 158 a, 158 b may be arranged on the surface of a muscle orother tissue, in order to modulate a nerve embedded within the muscle orother tissue. Thus, tissue may be interposed between modulationelectrodes 158 a, 158 b and a nerve to be modulated. Modulationelectrodes 158 a, 158 b may be spaced away from a nerve to be modulated.The structure and configuration of modulation electrodes 158 a, 158 bmay play an important role in determining whether modulation of a nerve,which is spaced a certain distance away from the electrodes, may beachieved.

Electrode configurations A, B, and C show that when modulationelectrodes 158 a, 158 b of a constant size are moved further apart, thedepth of the electric field facilitated by the electrodes increases. Thestrength of the electric field for a given configuration may varysignificantly depending on a location within the field. If a constantlevel of current is passed between modulation electrodes 158 a and 158b, however, the larger field area of configuration C may exhibit a loweroverall current density than the smaller field area of configuration A.A lower current density, in turn, implies a lower voltage potentialdifference between two points spaced equidistant from each other in thefield facilitated by configuration C relative to that of the fieldfacilitated by configuration A. Thus, while moving modulation electrodes158 a and 158 b farther from each other increases the depth of thefield, it also decreases the strength of the field. In order to modulatea nerve spaced away from modulation electrodes 158 a, 158 b, a distancebetween the electrodes may be selected in order to facilitate anelectric field of strength sufficient to surpass a membrane thresholdpotential of the nerve (and thereby modulate it) at the depth of thenerve. If modulation electrodes 158 a, 158 b are too close together, theelectric field may not extend deep enough into the tissue in order tomodulate a nerve located therein. If modulation electrodes 158 a, 158 bare too far apart, the electric field may be too weak to modulate thenerve at the appropriate depth.

Appropriate distances between modulation electrodes 158 a, 158 b, maydepend on an implant location and a nerve to be stimulated. For example,modulation point 901 is located at the same depth equidistant from thecenters of modulation electrodes 158 a, 158 b in each of configurationsA, B, and C. The figures illustrate that, in this example, configurationB is most likely to achieve the highest possible current density, andtherefore voltage potential, at modulation point 901. The field ofconfiguration A may not extend deeply enough, and the field ofconfiguration C may be too weak at that depth.

In some embodiments, modulation electrodes 158 a, 158 b may be spacedapart by about a distance of about 0.2 mm to 25 mm. In additionalembodiments, modulation electrodes 158 a, 158 b may be spaced apart by adistance of about 1 mm to 10 mm, or between 4 mm and 7 mm. In otherembodiments modulation electrodes 158 a, 158 b may be spaced apart bybetween approximately 6 mm and 7 mm.

Electrode configurations D, E, and F show that when modulationelectrodes 158 a, 158 b of a constant distance are changed in size, theshape of the electric field facilitated by the electrodes changes. If aconstant level of current is passed between when modulation electrodes158 a and 158 b, the smaller electrodes of configuration D mayfacilitate a deeper field than that of configurations E and F, althoughthe effect is less significant relative to changes in distance betweenthe electrodes. As noted above, the facilitated electric fields are notof uniform strength throughout, and thus the voltage potential atseemingly similar locations within each of the electric fields ofconfigurations D, E, and, F may vary considerably. Appropriate sizes ofmodulation electrodes 158 a, 158 b, may therefore depend on an implantlocation and a nerve to be stimulated.

In some embodiments, modulation electrodes 158 a, 158 b may have asurface area between approximately 0.01 mm² and 80 mm². In additionalembodiments, modulation electrodes 158 a, 158 b may have a surface areabetween approximately 0.1 mm² and 4 mm². In other embodiments modulationelectrodes 158 a, 158 b may have a surface area of between approximately0.25 mm² and 0.35 mm².

In some embodiments, modulation electrodes 158 a, 158 b may be arrangedsuch that the electrodes are exposed on a single side of carrier 161. Insuch an embodiment, an electric field is generated only on the side ofcarrier 161 with exposed electrical contacts. Such a configuration mayserve to reduce the amount of energy required to achieve neuralmodulation, because the entire electric field is generated on the sameside of the carrier as the nerve, and little or no current is wastedtraveling through tissue away from the nerve to be modulated. Such aconfiguration may also serve to make the modulation more selective. Thatis, by generating an electric field on the side of the carrier wherethere is a nerve to be modulated, nerves located in other areas oftissue (e.g. on the other side of the carrier from the nerve to bemodulated), may avoid being accidentally modulated.

As discussed above, the utilization of electric fields having electricalfield lines extending in a direction substantially parallel to thelongitudinal direction of a nerve to be modulated may serve to lower thepower requirements of modulation. This reduction in power requirementsmay permit the modulation of a nerve using less than 1.6 mA of current,less than 1.4 mA of current, less than 1.2 mA of current, less than 1 mAof current, less than 0.8 mA of current, less than 0.6 mA of current,less than 0.4 mA of current, and even less than 0.2 mA of current passedbetween modulation electrodes 158 a, 158 b.

Reducing the current flow required may have additional effects on theconfiguration of implant unit 110 and external unit 120. For example,the reduced current requirement may enable implant unit 110 to modulatea nerve without a requirement for a power storage unit, such as abattery or capacitor, to be implanted in conjunction with implant unit110. For example, implant unit 110 may be capable of modulating a nerveusing only the energy received via secondary antenna 152. Implant unit110 may be configured to serve as a pass through that directssubstantially all received energy to modulation electrodes 158 a and 158b for nerve modulation. Substantially all received energy may refer tothat portion of energy that is not dissipated or otherwise lost to theinternal components of implant unit 110. Finally, the reduction inrequired current may also serve to reduce the amount of energy requiredby external unit 120. External unit 120 may be configured to operatesuccessfully for an entire treatment session lasting from one to tenhours by utilizing a battery having a capacity of less than 240 mAh,less than 120 mAh, and even less than 60 mAh.

As discussed above, utilization of parallel fields may enable implantunit 110 to modulate nerves in a non-contacting fashion. Contactlessneuromodulation may increase the efficacy of an implanted implant unit110 over time compared to modulation techniques requiring contact with anerve or muscle to be modulated. Over time, implantable devices maymigrate within the body. Thus, an implantable device requiring nervecontact to initiate neural modulation may lose efficacy as the devicemoves within the body and loses contact with the nerve to be modulated.In contrast, implant unit 110, utilizing contactless modulation, maystill effectively modulate a nerve even if it moves toward, away, or toanother location relative to an initial implant location. Additionally,tissue growth and/or fibrosis may develop around an implantable device.This growth may serve to lessen or even eliminate the contact between adevice designed for contact modulation and a nerve to be modulated. Incontrast, implant unit 110, utilizing contactless modulation, maycontinue to effectively modulate a nerve if additional tissue formsbetween it and a nerve to be modulated.

Another feature enabled through the use of parallel fields is theability to modulate nerves of extremely small diameter. As the diameterof a nerve decreases, the electrical resistance of the nerve increases,causing the voltage required to induce an action potential to rise. Asdescribed above, the utilization of parallel electric fields permits theapplication of larger voltage potentials across nerves. This, in turn,may permit the modulation of smaller diameter nerves, requiring largervoltage potentials to induce action potentials. Nerves typically havereduced diameters at their terminal fibers, e.g. the distal ends, asthey extend away from the nerve trunk. Modulating these narrowerterminal fibers may permit more selective modulation. Larger nervetrunks typically carry many nerve fibers that may innervate severaldifferent muscles, and so inducing modulation of a nerve trunk may causeto the modulation of unintended nerve fibers, and thus the innervationand contraction of unintended muscles. Selective modulation of terminalfibers may prevent such unintended muscle activity. In some embodiments,implant unit 110 may be configured to modulate nerves having diametersof less than 2 mm, less than 1 mm, less than 500 microns, less than 200microns, less than 100 microns, less than 50 microns, and even less than25 microns.

Whether a field inducing signal constitutes a modulation signal(resulting in an electric field that may cause nerve modulation) or asub-modulation signal (resulting in an electric field not intended tocause nerve modulation) may ultimately be controlled by processor 144 ofexternal unit 120. For example, in certain situations, processor 144 maydetermine that nerve modulation is appropriate. Under these conditions,processor 144 may cause signal source 144 and amplifier 146 to generatea modulation control signal on primary antenna 150 (i.e., a signalhaving a magnitude and/or duration selected such that a resultingsecondary signal on secondary antenna 152 will provide a modulationsignal at implant electrodes 158 a and 158 b).

Processor 144 may be configured to limit an amount of energy transferredfrom external unit 120 to implant unit 110. For example, in someembodiments, implant unit 110 may be associated with a threshold energylimit that may take into account multiple factors associated with thepatient and/or the implant. For example, in some cases, certain nervesof a patient should receive no more than a predetermined maximum amountof energy to minimize the risk of damaging the nerves and/or surroundingtissue. Additionally, circuitry 180 of implant unit 110 may includecomponents having a maximum operating voltage or power level that maycontribute to a practical threshold energy limit of implant unit 110.Processor 144 may be configured to account for such limitations whensetting the magnitude and/or duration of a primary signal to be appliedto primary antenna 150.

In addition to determining an upper limit of power that may be deliveredto implant unit 110, processor 144 may also determine a lower powerthreshold based, at least in part, on an efficacy of the deliveredpower. The lower power threshold may be computed based on a minimumamount of power that enables nerve modulation (e.g., signals havingpower levels above the lower power threshold may constitute modulationsignals while signals having power levels below the lower powerthreshold may constitute sub-modulation signals).

A lower power threshold may also be measured or provided in alternativeways. For example, appropriate circuitry or sensors in the implant unit110 may measure a lower power threshold. A lower power threshold may becomputed or sensed by an additional external device, and subsequentlyprogrammed into processor 144, or programmed into implant unit 110.Alternatively, implant unit 110 may be constructed with circuitry 180specifically chosen to generate signals at the electrodes of at leastthe lower power threshold. In still another embodiment, an antenna ofexternal unit 120 may be adjusted to accommodate or produce a signalcorresponding to a specific lower power threshold. The lower powerthreshold may vary from patient to patient, and may take into accountmultiple factors, such as, for example, modulation characteristics of aparticular patient's nerve fibers, a distance between implant unit 110and external unit 120 after implantation, and the size and configurationof implant unit components (e.g., antenna and implant electrodes), etc.

Processor 144 may also be configured to cause application ofsub-modulation control signals to primary antenna 150. Suchsub-modulation control signals may include an amplitude and/or durationthat result in a sub-modulation signal at electrodes 158 a, 158 b. Whilesuch sub-modulation control signals may not result in nerve modulation,such sub-modulation control signals may enable feedback-based control ofthe nerve modulation system. That is, in some embodiments, processor 144may be configured to cause application of a sub-modulation controlsignal to primary antenna 150. This signal may induce a secondary signalon secondary antenna 152, which, in turn, induces a primary coupledsignal component on primary antenna 150.

To analyze the primary coupled signal component induced on primaryantenna 150, external unit 120 may include a feedback circuit 148 (e.g.,a signal analyzer or detector, etc.), which may be placed in direct orindirect communication with primary antenna 150 and processor 144.Sub-modulation control signals may be applied to primary antenna 150 atany desired periodicity. In some embodiments, the sub-modulation controlsignals may be applied to primary antenna 150 at a rate of one everyfive seconds (or longer). In other embodiments, the sub-modulationcontrol signals may be applied more frequently (e.g., once every twoseconds, once per second, once per millisecond, once per nanosecond, ormultiple times per second). Further, it should be noted that feedbackmay also be received upon application of modulation control signals toprimary antenna 150 (i.e., those that result in nerve modulation), assuch modulation control signals may also result in generation of aprimary coupled signal component on primary antenna 150.

The primary coupled signal component may be fed to processor 144 byfeedback circuit 148 and may be used as a basis for determining a degreeof coupling between primary antenna 150 and secondary antenna 152. Thedegree of coupling may enable determination of the efficacy of theenergy transfer between two antennas. Processor 144 may also use thedetermined degree of coupling in regulating delivery of power to implantunit 110.

Processor 144 may be configured with any suitable logic for determininghow to regulate power transfer to implant unit 110 based on thedetermined degree of coupling. For example, where the primary coupledsignal component indicates that a degree of coupling has changed from abaseline coupling level, processor 144 may determine that secondaryantenna 152 has moved with respect to primary antenna 150 (either incoaxial offset, lateral offset, or angular offset, or any combination).Such movement, for example, may be associated with a movement of theimplant unit 110, and the tissue that it is associated with based on itsimplant location. Thus, in such situations, processor 144 may determinethat modulation of a nerve in the patient's body is appropriate. Moreparticularly, in response to an indication of a change in coupling,processor 144, in some embodiments, may cause application of amodulation control signal to primary antenna 150 in order to generate amodulation signal at implant electrodes 158 a, 158 b, e.g., to causemodulation of a nerve of the patient.

In an embodiment for the treatment of a sleep breathing disorder,movement of an implant unit 110 may be associated with movement of thetongue, which may indicate snoring, the onset of a sleep apnea event ora sleep apnea precursor. Each of these conditions may require thestimulation of the genioglossus muscle of the patient to relieve oravert the event. Such stimulation may result in contraction of themuscle and movement of the patient's tongue away from the patient'sairway.

In embodiments for the treatment of head pain, including migraines,processor 144 may be configured to generate a modulation control signalbased on a signal from a user, for example, or a detected level ofneural activity in a sensory neuron (e.g. the greater occipital nerve ortrigeminal nerve) associated with head pain. A modulation control signalgenerated by the processor and applied to the primary antenna 150 maygenerate a modulation signal at implant electrodes 158 a, 158 b, e.g.,to cause inhibition or blocking of a sensory nerve of the patient. Suchinhibition or blocking may decrease or eliminate the sensation of painfor the patient.

In embodiments for the treatment of hypertension, processor 144 may beconfigured to generate a modulation control signal based on, forexample, pre-programmed instructions and/or signals from an implantindicative of blood pressure. A modulation control signal generated bythe processor and applied to the primary antenna 150 may generate amodulation signal at implant electrodes 158 a, 158 b, e.g., to causeeither inhibition or stimulation of nerve of a patient, depending on therequirements. For example, a neuromodulator placed in a carotid arteryor jugular artery (i.e. in the vicinity of a carotid baroreceptor), mayreceive a modulation control signal tailored to induce a stimulationsignal at the electrodes, thereby causing the glossopharyngeal nerveassociated with the carotid baroreceptors to fire at an increased ratein order to signal the brain to lower blood pressure. Similar modulationof the glossopharyngeal nerve may be achieved with a neuromodulatorimplanted in a subcutaneous location in a patient's neck or behind apatient's ear. A neuromodulator place in a renal artery may receive amodulation control signal tailored to cause an inhibiting or blockingsignal at the electrodes, thereby inhibiting a signal to raise bloodpressure carried from the renal nerves to the kidneys.

Modulation control signals may include stimulation control signals, andsub-modulation control signals may include sub-stimulation controlsignals. Stimulation control signals may have any amplitude, pulseduration, or frequency combination that results in a stimulation signalat electrodes 158 a, 158 b. In some embodiments (e.g., at a frequency ofbetween about 6.5-13.6 MHz), stimulation control signals may include apulse duration of greater than about 50 microseconds and/or an amplitudeof approximately 0.5 amps, or between 0.1 amps and 1 amp, or between0.05 amps and 3 amps. Sub-stimulation control signals may have a pulseduration less than about 500, or less than about 200 nanoseconds and/oran amplitude less than about 1 amp, 0.5 amps, 0.1 amps, 0.05 amps, or0.01 amps. Of course, these values are meant to provide a generalreference only, as various combinations of values higher than or lowerthan the exemplary guidelines provided may or may not result in nervestimulation.

In some embodiments, stimulation control signals may include a pulsetrain, wherein each pulse includes a plurality of sub-pulses. FIG. 17depicts the composition of an exemplary modulation pulse train. Such apulse train 1010 may include a plurality of modulation pulses 1020,wherein each modulation pulse 1020 may include a plurality of modulationsub-pulses 1030. FIG. 10 is exemplary only, at a scale appropriate forillustration, and is not intended to encompass all of the variouspossible embodiments of a modulation pulse train, discussed in greaterdetail below. An alternating current signal (e.g., at a frequency ofbetween about 6.5-13.6 MHz) may be used to generate a pulse train 1010,as follows. A sub-pulse 1030 may have a pulse duration of between 50-250microseconds, or a pulse duration of between 1 microsecond and 2milliseconds, during which an alternating current signal is turned on.For example, a 200 microsecond sub-pulse 1030 of a 10 MHz alternatingcurrent signal will include approximately 2000 periods. Each modulationpulse 1020 may, in turn, have a pulse duration 1040 of between 100 and500 milliseconds, during which sub-pulses 1030 occur at a frequency ofbetween 25 and 100 Hz. Thus, a modulation pulse 1020 may include betweenabout 2.5 and 50 modulation sub-pulses 1030. In some embodiments, amodulation 1020 pulse may include between about 5 and 15 modulationsub-pulses 1030. For example, a 200 millisecond modulation pulse 1020 of50 Hz modulation sub-pulses 1030 will include approximately 10modulation sub-pulses 1030. Finally, in a modulation pulse train 1010,each modulation pulse 1020 may be separated from the next by a temporalspacing 1050 of between 0.2 and 2 seconds. For example, in a pulse train1010 of 200 millisecond pulse duration 1040 modulation pulses 1020, eachseparated by a 1.3 second temporal spacing 1050 from the next, a newmodulation pulse 1020 will occur every 1.5 seconds. The frequency ofmodulation pulses 1020 may also be timed to in accordance withphysiological events of the subject. For example, modulation pulses 1020may occur at a frequency chosen from among any multiple of a breathingfrequency, such as four, eight, or sixteen. In another example,modulation pulses 1020 may be temporally spaced so as not to permit acomplete relaxation of a muscle after causing a muscular contraction.The pulse duration 1040 of modulation pulses 1020 and the temporalspacing 1050 between modulation pulses 1020 in a pulse train 1010 may bemaintained for a majority of the modulation pulses 1020, or may bevaried over the course of a treatment session according to a subject'sneed. Such variations may also be implemented for the modulationsub-pulse duration and temporal spacing.

Pulse train 1010 depicts a primary signal pulse train, as generated byexternal unit 120. In some embodiments, the primary signal may result ina secondary signal on the secondary antenna 152 of implant unit 110.This signal may be converted to a direct current signal for delivery tomodulation electrodes 158 a, 158 b. In this situation, the generation ofmodulation sub-pulse 1030 may result in the generation and delivery of asquare wave of a similar duration as modulation sub-pulse 1030 tomodulation electrodes 158 a, 158 b.

In an embodiment for the treatment of sleep disordered breathing,modulation pulses 1020 and modulation sub-pulses 1030 may includestimulation pulses and stimulation sub-pulses adapted to cause neuralstimulation. A pulse train 1010 of this embodiment may be utilized, forexample, to provide ongoing stimulation during a treatment session.Ongoing stimulation during a treatment session may include transmissionof the pulse train for at least 70%, at least 80%, at least 90%, and atleast 99% of the treatment session. In the context of sleep disorderedbreathing, a treatment session may be a period of time during which asubject is asleep and in need of treatment to prevent sleep disorderedbreathing. Such a treatment session may last anywhere from about threeto ten hours. A treatment session may include as few as approximately4,000 and as many as approximately 120,000 modulation pulses 1020. Insome embodiments, a pulse train 1010 may include at least 5,000, atleast 10,000, and at least 100,000 modulation pulses 1020. In thecontext of other conditions to which neural modulators of the presentdisclosure are applied, a treatment session may be of varying lengthaccording to the duration of the treated condition.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoring oneor more aspects of the primary coupled signal component received throughfeedback circuit 148. In some embodiments, processor 144 may determine adegree of coupling between primary antenna 150 and secondary antenna 152by monitoring a voltage level associated with the primary coupled signalcomponent, a current level, or any other attribute that may depend onthe degree of coupling between primary antenna 150 and secondary antenna152. For example, in response to periodic sub-modulation signals appliedto primary antenna 150, processor 144 may determine a baseline voltagelevel or current level associated with the primary coupled signalcomponent. This baseline voltage level, for example, may be associatedwith a range of movement of the patient's tongue when a sleep apneaevent or its precursor is not occurring, e.g. during normal breathing.As the patient's tongue moves toward a position associated with a sleepapnea event or its precursor, the coaxial, lateral, or angular offsetbetween primary antenna 150 and secondary antenna 152 may change. As aresult, the degree of coupling between primary antenna 150 and secondaryantenna 152 may change, and the voltage level or current level of theprimary coupled signal component on primary antenna 150 may also change.Processor 144 may be configured to recognize a sleep apnea event or itsprecursor when a voltage level, current level, or other electricalcharacteristic associated with the primary coupled signal componentchanges by a predetermined amount or reaches a predetermined absolutevalue.

FIG. 18 provides a graph that illustrates this principle in more detail.For a two-coil system where one coil receives a radio frequency (RF)drive signal, graph 200 plots a rate of change in induced current in thereceiving coil as a function of coaxial distance between the coils. Forvarious coil diameters and initial displacements, graph 200 illustratesthe sensitivity of the induced current to further displacement betweenthe coils, moving them either closer together or further apart. It alsoindicates that, overall, the induced current in the secondary coil willdecrease as the secondary coil is moved away from the primary, drivecoil, i.e. the rate of change of induced current, in mA/mm, isconsistently negative. The sensitivity of the induced current to furtherdisplacement between the coils varies with distance. For example, at aseparation distance of 10 mm, the rate of change in current as afunction of additional displacement in a 14 mm coil is approximately −6mA/mm. If the displacement of the coils is approximately 22 mm, the rateof change in the induced current in response to additional displacementis approximately −11 mA/mm, which corresponds to a local maximum in therate of change of the induced current. Increasing the separationdistance beyond 22 mm continues to result in a decline in the inducedcurrent in the secondary coil, but the rate of change decreases. Forexample, at a separation distance of about 30 mm, the 14 mm coilexperiences a rate of change in the induced current in response toadditional displacement of about −8 mA/mm. With this type ofinformation, processor 144 may be able to determine a particular degreeof coupling between primary antenna 150 and secondary antenna 152, atany given time, by observing the magnitude and/or rate of change in themagnitude of the current associated with the primary coupled signalcomponent on primary antenna 150.

Processor 144 may be configured to determine a degree of couplingbetween primary antenna 150 and secondary antenna 152 by monitoringother aspects of the primary coupled signal component. For example, insome embodiments, a residual signal, or an echo signal, may bemonitored. As shown in FIG. 14, circuitry 180 in implant unit 110 mayinclude inductors, capacitors, and resistors, and thus may constitute anLRC circuit. As described in greater detail above, when external unit120 transmits a modulation (or sub-modulation) control signal, acorresponding signal is developed on secondary antenna 152. The signaldeveloped on secondary antenna 152 causes current to flow in circuitry180 of implant unit 110, exciting the LRC circuit. When excited the LRCcircuit may oscillate at its resonant frequency, related to the valuesof the L (inductance), R (resistance), and C (capacitance values in thecircuit). When processor 144 discontinues generating the control signal,both the oscillating signal on primary antenna 150 and the oscillatingsignal on secondary antenna 152 may decay over a period of time as thecurrent is dissipated. As the oscillating signal on the secondaryantenna 152 decays, so too does the coupled feedback signal received byprimary antenna 150. Thus, the decaying signal in circuitry 180 ofimplant unit 110 may be monitored by processor 144 of external unit 120.This monitoring may be further facilitated by configuring the circuitry170 of external unit 120 to allow the control signal generated inprimary antenna 150 to dissipate faster than the signal in the implantunit 110. Monitoring the residual signal and comparing it to expectvalues of a residual signal may provide processor 144 with an indicationof a degree of coupling between primary antenna 150 and secondaryantenna 152.

Monitoring the decaying oscillating signal in the implant unit 110 mayalso provide processor 144 information about the performance of implantunit 110. Processor 144 may be configured to compare the parameters ofthe control signal with the parameters of the detected decaying implantsignal. For example, an amplitude of the decaying signal is proportionalto the amount of energy remaining in implant unit 110; by comparing anamount of energy transmitted in the control signal with an amount ofenergy remaining in the implant, processor 144 may determine a level ofpower consumption in the implant. Further, by comparing a level of powerconsumption in the implant to a detected amount of tongue movement,processor 144 may determine an efficacy level of transmitted modulationsignals. Monitoring the residual, or echo signals, in implant unit 110may permit the implementation of several different features. Thus,processor 144 may be able to determine information including powerconsumption in implant unit 110, current delivery to the tissue byimplant unit 110, energy delivery to implant unit 110, functionality ofimplant unit 110, and other parameters determinable through residualsignal analysis

Processor 144 may be configured to monitor the residual implant signalin a diagnostic mode. For example, if processor 144 detects no residualsignal in implant unit 110 after transmission of a control signal, itmay determine that implant unit 110 is unable to receive any type oftransmission, and is not functioning. In such a case, processor 144 maycause a response that includes an indication to a user that implant unit110 is not functioning properly. Such an indication may be in the formof, e.g., an audible or visual alarm. In another potential malfunction,if processor 144 detects a residual signal in the implant that is higherthan expected, it may determine that, while implant unit is receiving atransmitted control signal, the transmitted energy is not beingtransferred to the tissue by electrodes 158 a, 158 b, at an appropriaterate.

Processor 144 may also be configured to implement a treatment protocolincluding the application of a desired target current level to beapplied by the modulation electrodes (e.g., 1 mA). Even if themodulation control signal delivers a signal of constant amplitude, thedelivered current may not remain stable. The coupled feedback signaldetected by primary antenna 150 may be used as the basis for feedbackcontrol of the implant unit to ensure that the implant delivers a stable1 mA current during each application of a modulation control signal.Processor 144, by analyzing the residual signal in the implant, maydetermine an amount of current delivered during the application of amodulation control signal. Processor 144 may then increase or decreasethe amplitude of the modulation control signal based on the determinedinformation about the delivered current. Thus, the modulation controlsignal applied to primary antenna 150 may be adjusted until the observedamplitude of the echo signal indicates that the target current level hasbeen achieved.

In some embodiments, processor 144 may be configured to alter atreatment protocol based on detected efficacy during a therapy period.As described above, processor 144 may be configured, through residualsignal analysis, to determine the amount of current, power, or energydelivered to the tissue through electrodes 158 a, 158 b. Processor 144may be configured to correlate the detected amount of tongue movement asa result of a modulation control signal with the amount of powerultimately delivered to the tissue. Thus, rather than comparing theeffects of signal transmission with the amount of power or energytransmitted (which processor 144 may also be configured to do),processor 144 may compare the effects of signal transmission with theamount of power delivered. By comparing modulating effects with powerdelivered, processor 144 may be able to more accurately optimize amodulation signal.

The residual signal feedback methods discussed above may be applied toany of several other embodiments of the disclosure as appropriate. Forexample, information gathered through residual signal feedback analysismay be included in the information stored in memory unit 143 andtransmitted to a relay or final destination via communications interface145 of external unit 120. In another example, the above describedresidual signal feedback analysis may be incorporated into methodsdetecting tongue movement and tongue vibration.

In some embodiments, an initially detected coupling degree may establisha baseline range when the patient attaches external unit 120 to theskin. Presumably, while the patient is awake, the tongue is not blockingthe patient's airway and moves with the patients breathing in a naturalrange, where coupling between primary antenna 150 and secondary antenna152 may be within a baseline range. A baseline coupling range mayencompass a maximum coupling between primary antenna 150 and secondaryantenna 152. A baseline coupling range may also encompass a range thatdoes not include a maximum coupling level between primary antenna 150and secondary antenna 152. Thus, the initially determined coupling maybe fairly representative of a non-sleep apnea condition and may be usedby processor 144 as a baseline in determining a degree of couplingbetween primary antenna 150 and secondary antenna 152.

As the patient wears external unit 120, processor 144 may periodicallyscan over a range of primary signal amplitudes to determine currentvalues of coupling. If a periodic scan results in determination of adegree of coupling different from the baseline coupling, processor 144may determine that there has been a change from the baseline initialconditions.

By periodically determining a degree of coupling value, processor 144may be configured to determine, in situ, appropriate parameter valuesfor the modulation control signal that will ultimately result in nervemodulation. For example, by determining the degree of coupling betweenprimary antenna 150 and secondary antenna 152, processor 144 may beconfigured to select characteristics of the modulation control signal(e.g., amplitude, pulse duration, frequency, etc.) that may provide amodulation signal at electrodes 158 a, 158 b in proportion to orotherwise related to the determined degree of coupling. In someembodiments, processor 144 may access a lookup table or other datastored in a memory correlating modulation control signal parametervalues with degree of coupling. In this way, processor 144 may adjustthe applied modulation control signal in response to an observed degreeof coupling.

Additionally or alternatively, processor 144 may be configured todetermine the degree of coupling between primary antenna 150 andsecondary antenna 152 during modulation. The tongue, or other structureon or near which the implant is located, and thus implant unit 110, maymove as a result of modulation. Thus, the degree of coupling may changeduring modulation. Processor 144 may be configured to determine thedegree of coupling as it changes during modulation, in order todynamically adjust characteristics of the modulation control signalaccording to the changing degree of coupling. This adjustment may permitprocessor 144 to cause implant unit 110 to provide an appropriatemodulation signal at electrodes 158 a, 158 b throughout a modulationevent. For example, processor 144 may alter the primary signal inaccordance with the changing degree of coupling in order to maintain aconstant modulation signal, or to cause the modulation signal to bereduced in a controlled manner according to patient needs.

More particularly, the response of processor 144 may be correlated tothe determined degree of coupling. In situations where processor 144determines that the degree of coupling between primary antenna 150 andsecondary antenna has fallen only slightly below a predeterminedcoupling threshold (e.g., during snoring or during a small vibration ofthe tongue or other sleep apnea event precursor), processor 144 maydetermine that only a small response is necessary. Thus, processor 144may select modulation control signal parameters that will result in arelatively small response (e.g., a short stimulation of a nerve, smallmuscle contraction, etc.). Where, however, processor 144 determines thatthe degree of coupling has fallen substantially below the predeterminedcoupling threshold (e.g., where the tongue has moved enough to cause asleep apnea event), processor 144 may determine that a larger responseis required. As a result, processor 144 may select modulation controlsignal parameters that will result in a larger response. In someembodiments, only enough power may be transmitted to implant unit 110 tocause the desired level of response. In other words, processor 144 maybe configured to cause a metered response based on the determined degreeof coupling between primary antenna 150 and secondary antenna 152. Asthe determined degree of coupling decreases, processor 144 may causetransfer of power in increasing amounts. Such an approach may preservebattery life in the external unit 120, may protect circuitry 170 andcircuitry 180, may increase effectiveness in addressing the type ofdetected condition (e.g., sleep apnea, snoring, tongue movement, etc.),and may be more comfortable for the patient.

In some embodiments, processor 144 may employ an iterative process inorder to select modulation control signal parameters that result in adesired response level. For example, upon determining that a modulationcontrol signal should be generated, processor 144 may cause generationof an initial modulation control signal based on a set of predeterminedparameter values. If feedback from feedback circuit 148 indicates that anerve has been modulated (e.g., if an increase in a degree of couplingis observed), then processor 144 may return to a monitoring mode byissuing sub-modulation control signals. If, on the other hand, thefeedback suggests that the intended nerve modulation did not occur as aresult of the intended modulation control signal or that modulation ofthe nerve occurred but only partially provided the desired result (e.g.,movement of the tongue only partially away from the airway), processor144 may change one or more parameter values associated with themodulation control signal (e.g., the amplitude, pulse duration, etc.).

Where no nerve modulation occurred, processor 144 may increase one ormore parameters of the modulation control signal periodically until thefeedback indicates that nerve modulation has occurred. Where nervemodulation occurred, but did not produce the desired result, processor144 may re-evaluate the degree of coupling between primary antenna 150and secondary antenna 152 and select new parameters for the modulationcontrol signal targeted toward achieving a desired result. For example,where stimulation of a nerve causes the tongue to move only partiallyaway from the patient's airway, additional stimulation may be desired.Because the tongue has moved away from the airway, however, implant unit110 may be closer to external unit 120 and, therefore, the degree ofcoupling may have increased. As a result, to move the tongue a remainingdistance to a desired location may require transfer to implant unit 110of a smaller amount of power than what was supplied prior to the laststimulation-induced movement of the tongue. Thus, based on a newlydetermined degree of coupling, processor 144 can select new parametersfor the stimulation control signal aimed at moving the tongue theremaining distance to the desired location.

In one mode of operation, processor 144 may be configured to sweep overa range of parameter values until nerve modulation is achieved. Forexample, in circumstances where an applied sub-modulation control signalresults in feedback indicating that nerve modulation is appropriate,processor 144 may use the last applied sub-modulation control signal asa starting point for generation of the modulation control signal. Theamplitude and/or pulse duration (or other parameters) associated withthe signal applied to primary antenna 150 may be iteratively increasedby predetermined amounts and at a predetermined rate until the feedbackindicates that nerve modulation has occurred.

Processor 144 may be configured to determine or derive variousphysiologic data based on the determined degree of coupling betweenprimary antenna 150 and secondary antenna 152. For example, in someembodiments the degree of coupling may indicate a distance betweenexternal unit 120 and implant unit 110, which processor 144 may use todetermine a position of external unit 120 or a relative position of apatient's tongue. Monitoring the degree of coupling can also providesuch physiologic data as whether a patient's tongue is moving orvibrating (e.g., whether the patient is snoring), by how much the tongueis moving or vibrating, the direction of motion of the tongue, the rateof motion of the tongue, etc.

In response to any of these determined physiologic data, processor 144may regulate delivery of power to implant unit 110 based on thedetermined physiologic data. For example, processor 144 may selectparameters for a particular modulation control signal or series ofmodulation control signals for addressing a specific condition relatingto the determined physiologic data. If the physiologic data indicatesthat the tongue is vibrating, for example, processor 144 may determinethat a sleep apnea event is likely to occur and may issue a response bydelivering power to implant unit 110 in an amount selected to addressthe particular situation. If the tongue is in a position blocking thepatient's airway (or partially blocking a patient's airway), but thephysiologic data indicates that the tongue is moving away from theairway, processor 144 may opt to not deliver power and wait to determineif the tongue clears on its own. Alternatively, processor 144 maydeliver a small amount of power to implant unit 110 (e.g., especiallywhere a determined rate of movement indicates that the tongue is movingslowly away from the patient's airway) to encourage the tongue tocontinue moving away from the patient's airway or to speed itsprogression away from the airway.

In an embodiment for the treatment of snoring, processor 144 may beconfigured to determine when a subject is snoring based on a feedbacksignal that varies based on a breathing pattern of the subject. Thefeedback signal, may include, for example, the signal induced in theprimary antenna as a result of a sub-modulating signal transmitted tothe secondary antenna. In an embodiment for determining whether asubject is snoring, in addition to a tongue location, tongue movementmay be detected through a degree of coupling. Tongue movement, which mayinclude tongue velocity, tongue displacement, and tongue vibration, maybe indicative of snoring. Processor 144 may be configured to detect atongue movement pattern and compare the detected movement pattern toknown patterns indicative of snoring. For example, when a patientsnores, the tongue may vibrate in a range between 60-100 Hz, suchvibration may be detected by monitoring the coupling signal for a signalat a similar frequency. Such changes in the coupling signal may berelatively small compared to changes associated with larger movements ofthe tongue. Thus, snoring detection methods may be optimized to identifylow amplitude signals. A low amplitude signal between 60-100 Hz may thusconstitute a tongue movement pattern indicative of snoring. Additionalpatterns may also be detected.

Another exemplary feedback signal may include a signal obtained byexternal unit 120 about a snoring condition. For example, audio sensors,microphones, and/or piezoelectric devices may be incorporated intoexternal unit 120 to gather data about a potential snoring condition.Such sensors may detect sound vibrations traveling through the air andmay detect vibrations of the subject's body near the location of theexternal unit's contact with the skin. In still another embodiment, thefeedback signal may be provided by a thermistor, or other temperaturemeasuring device, positioned so as to measure a temperature in theairway.

In yet another embodiment, a feedback signal that varies based upon abreathing pattern of the subject may be provided by electromyographyelectrodes. Electromyography electrodes may detect electrical activityin muscles. Interpretation of this electrical activity may provideinformation about muscular contraction and muscle tone. During normalbreathing, subjects typically exhibit a pattern of muscular contractionsthat may be associated with the normal breathing, as muscles from theface, chin, neck, ribs, and diaphragm experience contractions insequence. Electromyography electrodes may be used to measure both thestrength and the pattern of muscular contractions during breathing.

In still another embodiment, an accelerometer located on, or otherwiseassociated with external unit 120 may be utilized as the feedback signalto detect snoring. Located on the neck, ribs, or diaphragm, anaccelerometer, by measuring external body movements, may detect asubject's breathing patterns. The accelerometer-detected breathingpatterns may be analyzed to detect deviations from a normal breathingpattern, such as breathing patterns indicating heightened or otherwisealtered effort.

In additional embodiments, multiple feedback signals may be utilized todetect snoring in various combinations. For example, processor 144 maybe configured such that, when a tongue movement pattern indicative ofsnoring is detected, sensors incorporated into external unit 120 arethen monitored for confirmation that a snoring condition is occurring.In another example, processor 144 may be configured to utilize sensorsin external unit 120 and/or an airway temperature measuring device todetect the presence of snoring, and then to detect and record the tonguemovement pattern associated with the snoring. In this way, processor 144may be configured to learn a tongue movement pattern associated withsnoring individual to a particular user.

Snoring may be correlated with heightened or otherwise altered breathingeffort. Any or all of the previously described feedback methods may beused to determine or detect a heightened or otherwise altered breathingeffort. Detection of such heightened or otherwise altered breathingeffort may be used by processor 144 to determine that snoring isoccurring.

If snoring is detected, processor 144 may be configured to cause ahypoglossal nerve modulation control signal to be applied to the primaryantenna in order to wirelessly transmit the hypoglossal nerve modulationcontrol signal to the secondary antenna of implant unit 110. Thus, inresponse to a detection of snoring, the processor may cause thehypoglossal nerve to be modulated. Hypoglossal nerve modulation maycause a muscular contraction of the genioglossus muscle, which may inturn alleviate the snoring condition.

The scenarios described are exemplary only. Processor 144 may beconfigured with software and/or logic enabling it to address a varietyof different physiologic scenarios with particularity. In each case,processor 144 may be configured to use the physiologic data to determinean amount of power to be delivered to implant unit 110 in order tomodulate nerves associated with the tongue with the appropriate amountof energy.

The disclosed embodiments may be used in conjunction with a method forregulating delivery of power to an implant unit. The method may includedetermining a degree of coupling between primary antenna 150 associatedwith external unit 120 and secondary antenna 152 associated with implantunit 110, implanted in the body of a patient. Determining the degree ofcoupling may be accomplished by processor 144 located external toimplant unit 110 and that may be associated with external unit 120.Processor 144 may be configured to regulate delivery of power from theexternal unit to the implant unit based on the determined degree ofcoupling.

As previously discussed, the degree of coupling determination may enablethe processor to further determine a location of the implant unit. Themotion of the implant unit may correspond to motion of the body partwhere the implant unit may be attached. This may be consideredphysiologic data received by the processor. The processor may,accordingly, be configured to regulate delivery of power from the powersource to the implant unit based on the physiologic data. In alternativeembodiments, the degree of coupling determination may enable theprocessor to determine information pertaining to a condition of theimplant unit. Such a condition may include location as well asinformation pertaining to an internal state of the implant unit. Theprocessor may, according to the condition of the implant unit, beconfigured to regulate delivery of power from the power source to theimplant unit based on the condition data.

In some embodiments, implant unit 110 may include a processor located onthe implant. A processor located on implant unit 110 may perform all orsome of the processes described with respect to the at least oneprocessor associated with an external unit. For example, a processorassociated with implant unit 110 may be configured to receive a controlsignal prompting the implant controller to turn on and cause amodulation signal to be applied to the implant electrodes for modulatinga nerve. Such a processor may also be configured to monitor varioussensors associated with the implant unit and to transmit thisinformation back to and external unit. Power for the processor unit maybe supplied by an onboard power source or received via transmissionsfrom an external unit.

In other embodiments, implant unit 110 may be self-sufficient, includingits own power source and a processor configured to operate the implantunit 110 with no external interaction. For example, with a suitablepower source, the processor of implant unit 110 could be configured tomonitor conditions in the body of a subject (via one or more sensors orother means), determining when those conditions warrant modulation of anerve, and generate a signal to the electrodes to modulate a nerve. Thepower source could be regenerative based on movement or biologicalfunction; or the power sources could be periodically rechargeable froman external location, such as, for example, through induction.

FIG. 19 illustrates an exemplary implantation location for implant unit110. FIG. 19 depicts an implantation location in the vicinity of agenioglossus muscle 1060 that may be accessed through derma on anunderside of a subject's chin. FIG. 19 depicts hypoglossal nerve (i.e.cranial nerve XII). The hypoglossal nerve 1051, through its lateralbranch 1053 and medial branch 1052, innervates the muscles of the tongueand other glossal muscles, including the genioglossus 1060, thehyoglossus, 1062, myelohyoid (not shown) and the geniohyoid 1061muscles. The myelohyoid muscle, not pictured in FIG. 19, forms the floorof the oral cavity, and wraps around the sides of the genioglossusmuscle 1060. The horizontal compartment of the genioglossus 1060 ismainly innervated by the medial terminal fibers 1054 of the medialbranch 1052, which diverges from the lateral branch 1053 at terminalbifurcation 1055. The distal portion of medial branch 1052 thenvariegates into the medial terminal fibers 1054. Contraction of thehorizontal compartment of the genioglossus muscle 1060 may serve to openor maintain a subject's airway. Contraction of other glossal muscles mayassist in other functions, such as swallowing, articulation, and openingor closing the airway. Because the hypoglossal nerve 1051 innervatesseveral glossal muscles, it may be advantageous, for OSA treatment, toconfine modulation of the hypoglossal nerve 1051 to the medial branch1052 or even the medial terminal fibers 1054 of the hypoglossal nerve1051. In this way, the genioglossus muscle, most responsible for tonguemovement and airway maintenance, may be selectively targeted forcontraction inducing neuromodulation. Alternatively, the horizontalcompartment of the genioglossus muscle may be selectively targeted. Themedial terminal fibers 1054 may, however, be difficult to affect withneuromodulation, as they are located within the fibers of thegenioglossus muscle 1061. Embodiments of the present inventionfacilitate modulation the medial terminal fibers 1054, as discussedfurther below.

In some embodiments, implant unit 110, including at least one pair ofmodulation electrodes, e.g. electrodes 158 a, 158 b, and at least onecircuit may be configured for implantation through derma (i.e. skin) onan underside of a subject's chin. When implanted through derma on anunderside of a subject's chin, an implant unit 110 may be locatedproximate to medial terminal fibers 1054 of the medial branch 1052 of asubject's hypoglossal nerve 1051. An exemplary implant location 1070 isdepicted in FIG. 19.

In some embodiments, implant unit 110 may be configured such that theelectrodes 158 a, 158 b cause modulation of at least a portion of thesubject's hypoglossal nerve through application of an electric field toa section of the hypoglossal nerve 1051 distal of a terminal bifurcation1055 to lateral and medial branches 1053, 1052 of the hypoglossal nerve1051. In additional or alternative embodiments, implant unit 110 may belocated such that an electric field extending from the modulationelectrodes 158 a, 158 b can modulate one or more of the medial terminalfibers 1054 of the medial branch 1052 of the hypoglossal nerve 1051.Thus, the medial branch 1053 or the medial terminal fibers 1054 may bemodulated so as to cause a contraction of the genioglossus muscle 1060,which may be sufficient to either open or maintain a patient's airway.When implant unit 110 is located proximate to the medial terminal fibers1054, the electric field may be configured so as to cause substantiallyno modulation of the lateral branch of the subject's hypoglossal nerve1051. This may have the advantage of providing selective modulationtargeting of the genioglossus muscle 1060.

As noted above, it may be difficult to modulate the medial terminalfibers 1054 of the hypoglossal nerve 1051 because of their locationwithin the genioglossus muscle 1060. Implant unit 110 may be configuredfor location on a surface of the genioglossus muscle 1060. Electrodes158 a, 158 b, of implant unit 110 may be configured to generate aparallel electric field 1090, sufficient to cause modulation of themedial terminal branches 1054 even when electrodes 158 a, 158 b are notin contact with the fibers of the nerve. That is, the anodes and thecathodes of the implant may be configured such that, when energized viaa circuit associated with the implant 110 and electrodes 158 a, 158 b,the electric field 1090 extending between electrodes 158 a, 158 b may bein the form of a series of substantially parallel arcs extending throughand into the muscle tissue on which the implant is located. A pair ofparallel line electrodes or two series of circular electrodes may besuitable configurations for producing the appropriate parallel electricfield lines. Thus, when suitably implanted, the electrodes of implantunit 110 may modulate a nerve in a contactless fashion, through thegeneration of parallel electric field lines.

Furthermore, the efficacy of modulation may be increased by an electrodeconfiguration suitable for generating parallel electric field lines thatrun partially or substantially parallel to nerve fibers to be modulated.In some embodiments, the current induced by parallel electric fieldlines may have a greater modulation effect on a nerve fiber if theelectric field lines 1090 and the nerve fibers to be modulated arepartially or substantially parallel. The inset illustration of FIG. 19depicts electrodes 158 a and 158 b generating electric field lines 1090(shown as dashed lines) substantially parallel to medial terminal fibers1054.

In order to facilitate the modulation of the medial terminal fibers1054, implant unit 110 may be designed or configured to ensure theappropriate location of electrodes when implanted. An exemplaryimplantation is depicted in FIG. 20.

For example, a flexible carrier 161 of the implant may be configuredsuch that at least a portion of a flexible carrier 161 of the implant islocated at a position between the genioglossus muscle 1060 and thegeniohyoid muscle 1061. Flexible carrier 161 may be further configuredto permit at least one pair of electrodes arranged on flexible carrier161 to lie between the genioglossus muscle 1060 and the myelohyoidmuscle. Either or both of the extensions 162 a and 162 b of elongate arm161 may be configured adapt to a contour of the genioglossus muscle.Either or both of the extensions 162 a and 162 b of elongate arm 161 maybe configured to extend away from the underside of the subject's chinalong a contour of the genioglossus muscle 1060. Either or both ofextension arms 162 a, 162 b may be configured to wrap around thegenioglossus muscle when an antenna 152 is located between thegenioglossus 1060 and geniohyoid muscle 1061. In such a configuration,antenna 152 may be located in a plane substantially parallel with aplane defined by the underside of a subject's chin, as shown in FIG. 20.

Flexible carrier 161 may be configured such that the at least one pairof spaced-apart electrodes can be located in a space between thesubject's genioglossus muscle and an adjacent muscle. Flexible carrier161 may be configured such that at least one pair of modulationelectrodes 158 a, 158 b is configured for implantation adjacent to ahorizontal compartment 1065 of the genioglossus muscle 1060. Thehorizontal compartment 1065 of the genioglossus 1060 is depicted in FIG.20 and is the portion of the muscle in which the muscle fibers run in asubstantially horizontal, rather than vertical, oblique, or transversedirection. At this location, the hypoglossal nerve fibers run betweenand in parallel to the genioglossus muscle fibers. In such a location,implant unit 110 may be configured such that the modulation electrodesgenerate an electric field substantially parallel to the direction ofthe muscle fibers, and thus, the medial terminal fibers 1054 of thehypoglossal nerve in the horizontal compartment.

As described above, implant unit 110 may include electrodes 158 a, 158 bon both extensions 162 a, 162 b, of extension arm 162. In such aconfiguration, implant unit 110 may be configured for bilateralhypoglossal nerve stimulation. The above discussion has focused on asingle hypoglossal nerve 1051. The body contains a pair of hypoglossalnerves 1051, on the left and right sides, each innervating muscles onits side. When a single hypoglossal nerve 1051 is modulated, it maycause stronger muscular contractions on the side of the body with whichthe modulated hypoglossal nerve is associated. This may result inasymmetrical movement of the tongue. When configured for bilateralstimulation, implant unit 110 may be able to stimulate both a left and aright hypoglossal nerve 1051, causing more symmetric movement of thetongue and more symmetric airway dilation. As illustrated in FIGS. 11 aand 11 b, flexible carrier 161 may be sized and shaped for implantationin a vicinity of a hypoglossal nerve to be modulated such that the firstpair of modulation electrodes is located to modulate a first hypoglossalnerve on a first side of the subject and the second pair of modulationelectrodes is located to modulate a second hypoglossal nerve on a secondside of the subject.

Bilateral stimulation protocols may include various sequences ofmodulation. For example, both pairs of modulation electrodes may beactivated together to provide a stronger muscular response in thesubject. In another example, the modulation electrodes may be activatedin an alternating sequence, first one, and then the other. Such asequence may reduce muscle or neuronal fatigue during a therapy period,and may reduce the diminishment of sensitivity that can occur in aneuron subject to a constant modulation signal. In still anotherexample, the modulation electrodes may be activated in an alternatingsequence that includes polarity reversals of the electric field. In suchan embodiment, one pair of electrodes may be activated with aneuromuscular modulating electric field having a polarity configured tocause a muscular contraction, while the other pair of electrodes may beactivated with a field having a reversed polarity. By alternating thepolarity, it may be possible to reduce short term neuronal fatigue andpossible to minimize or eliminate long term neuronal damage. In someconfigurations, extensions 162 a and 162 b may act as elongated armsextending from a central portion of flexible carrier 161 of implant unit110. The elongated arms may be configured to form an open endedcurvature around a muscle, with a nerve to be stimulated, e.g. ahypoglossal nerve, located within the curvature formed by the elongatedarms. Such a configuration may also include a stiffening portion locatedon or within flexible carrier 161. Such a stiffening portion maycomprise a material that is stiffer than a material of flexible carrier161. The stiffening portion may be preformed in a shape to betteraccommodate conforming flexible carrier 161 to a muscle of thesubject—such as a genioglossus muscle. The stiffening portion may alsobe capable of plastic deformation, so as to permit a surgeon to modifythe curvature of the flexible carrier 161 prior to implantation.

The diameter of the curvature of the elongated arms may be significantlylarger than the diameter of the nerve to be stimulated, for example, 2,5, 10, 20, or more times larger. In some embodiments, a plurality ofnerves to be stimulated, for example a left hypoglossal nerve and aright hypoglossal nerve, may be located within the arc of curvatureformed by the elongated arms.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the present disclosure.

While this disclosure provides examples of the neuromodulation devicesemployed for the treatment of certain conditions, usage of the disclosedneuromodulation devices is not limited to the disclosed examples. Thedisclosure of uses of embodiments of the invention for neuromodulationare to be considered exemplary only. In its broadest sense, theinvention may be used in connection with the treatment of anyphysiological condition through neuromodulation. Alternative embodimentswill become apparent to those skilled in the art to which the presentinvention pertains without departing from its spirit and scope.Accordingly, the scope of the present invention is defined by theappended claims rather than the foregoing description.

What is claimed is:
 1. An implantable device, comprising: a flexiblecarrier configured for implantation in a subject; at least one pair ofmodulation electrodes associated with the carrier; an antenna configuredto receive an electrical signal disposed on the flexible carrier; acircuit electrically coupling the antenna to the at least one pair ofmodulation electrodes; and a rigid housing, wherein at least one of theantenna and the circuit are located within the rigid housing.
 2. Theimplantable device of claim 1, further comprising a silicone layerencapsulating the rigid housing.
 3. The implantable device of claim 2,further comprising a parylene layer disposed between the silicone layerand the rigid housing.
 4. The implantable device of claim 1, wherein therigid housing includes a plurality of conductive feedthroughs, thefeedthroughs providing electrical coupling between the circuit and themodulation electrodes.
 5. The implantable device of claim 1, wherein therigid housing includes at least one of ceramic, glass, and titanium.